For three seasons Chelsea have relied on the bull. In 120 matches that have yielded 59 goals, Diego Costa has scattered Premier League defenders out of his way like the parting crowds in Pamplona's annual Running of the Bull festival. A Brazilian named Diego who turns out for Spain was always going to be trouble.
Now it's the turn of the matador, Alvaro Morata.
Ernest Hemingway, who probably would have invented Costa if he didn't already exist and almost certainly would have loved him, wrote in the The Sun Also Rises: "Nobody ever lives their life all the way up except bullfighters." Morata, in scoring for Juventus in both legs of a UEFA Champions League semi-final against Real Madrid—who owned him at the time—to knock them out of the competition in 2015 is probably as close as a footballer has got in recent times to disproving Papa's theory.
He even had the cojones to return to the city of his birth for a second crack at making it at the Santiago Bernabeu. There's no shame in falling just short of dislodging any of Cristiano Ronaldo, Gareth Bale or Karim Benzema.
In his own understated way, the cold-eyed finisher is almost as fascinating as Costa. At 24, he arrives at Chelsea for a club-record £58 million fee on the back of a La Liga and Champions League double at Madrid. He has played in three of the last four European Cup finals, including last season's against Juventus to complete the circle.
Morata would have needed to charter an additional plane to bring his trophy cabinet to London, swelled as it is into double figures by two Spanish league titles, two Champions Leagues, two Scudettos, two Copa del Reys, two Coppa Italias, a UEFA Super Cup and a FIFA Club World Cup. He has also top-scored for Spain in a major tournament, leading the line ahead of Costa at Euro 2016.
He has the CV of a superstar yet arrives in England with almost as many question marks next to his name as ticks. Morata is a big-game player who hasn't played enough games, and he knows it.
Throughout his career to date, Morata has been the character actor whose name on the credits is a hallmark of a film's quality, but it is only when it is rolling down the screen that you can recall it. He's finally been cast as a leading man. Whether he can cut it may well define Chelsea's season.
A player who, by his own admission, can doubt himself at times, he should have the perfect manager in Antonio Conte.
For all the talk of Morata being Chelsea's second choice, with the sound of the summer being springs groaning under the weight of perpetual bed-hopping involving him, Romelu Lukaku, Jose Mourinho and Conte, they do seem a neat fit.
It was Conte who brought Morata to Juventus in 2014, before four days later surprising the whole of Italy by quitting his post.
Conte will have been impressed with how a 21-year-old kid in a foreign country made a real success of being left in Turin to work things out for himself. He went on to have the best season of his career.
The player certainly doesn't bear a grudge. In April, he gave a prescient interview with the Guardian's man in Spain, Sid Lowe, which was effectively two parts "come and get me," one part "I'm coming even if you don't want me."
"Conte is the manager who most 'bet' on me, without even ever having had me in his team. I'm very conscious of that: he bet on me for Juventus but left before I arrived; then he wanted me at Chelsea come what may. He knows me better than I could imagine, I'm sure, and that's important: it motivates you to work hard, train well.
"I feel indebted to him because he's the coach that most trusted in me, most wanted me, who made me feel I could perform at the highest level. And yet I've never had the fortune to actually work with him. I'm sure sooner or later I will.
"I can do a lot but I need to play more and for someone to really back me. I'm no longer the youngest, I'm 24, it's a big moment."
It doesn't appear as though he is going to spend the season crying himself to sleep with a laminated photograph of Mourinho tucked under his pillow. In terms of settling in, Chelsea's burgeoning Spanish contingent should help him acclimatize to life in England.
When Conte delivered Costa a fait accompli over his future earlier in summer, via text message, it was as cold as it gets. A horse's head in a bull's bed, as it were. The Italian has said he made his mind up about Costa in January when the striker agitated for a move, having had his head turned by a combination of Chinese coin and former flame Atletico Madrid. That he managed to coax/con out of Costa enough match-winning displays to get Chelsea over the line in the second half of the season, says much about the manager's psychological cunning.
He may need it to tease out of Morata the world-class player that most even-handed observers would argue is definitely in there, waiting patiently. With a selfless work rate and willingness to mould his game to suit his team, he comes across as a real managers' player. Heavyweights Zinedine Zidane, Carlo Ancelotti, Massimiliano Allegri and Mourinho all speak of him in glowing terms.
In contrast, Costa's shtick is often so overblown it can render him little more than a caricature. In his most rumbustious periods, he veers into self-parody almost on a match-by-match basis. A casual flick of a horn impales an opposition centre-half as often as it results in a goal.
Yet the pantomime-villain routine, derided by the puritanical and terminally dull, has propelled Chelsea to two titles in three seasons. Costa delivered 20 league goals in each of them. Replacing him will not be anything like as straightforward as many seem to believe.
Much has been made of the fact last term was the first time in Morata's career he has got into double figures for league goals. Mightily as impressive as scoring 15 in just 14 starts (and a further 12 substitute appearances) surely is, and even withstanding some of the best strikers only really found their goalscoring groove around the same age as Morata, Conte has been the architect of enough title-winning sides to know a 20-goal-a-season player makes things a darn sight easier.
Still, 15 goals from 55 shots is some conversion rate. His record for Spain isn't half bad either; with nine goals in 21 games comparing favourably to Costa's five in 15. It all augurs well for the future, but there's a stark difference between potential and proven pedigree.
Though Morata's goals often come late in games, nine of his 20 last term came on or after the hour mark, it would be misleading to cast him purely as an opportunistic looter when defences have already been left ramshackle by Madrid's BBC front line.
In La Liga he was directly responsible for earning Madrid 13 points. For a little context, Ronaldo was credited with accruing an extra 14 points for his side, and he's got a lovely bronze bust. No player in the Premier League won more points than Costa, with nine of his goals having a decisive impact on matches.
If Morata is just a pickpocket, he deserves to be credited as being Fagan's top boy, at the very least.
Only Lionel Messi in the whole of La Liga bettered Morata's goals-per-minute ratio of 15 in 1,334, which works out at one every 89 minutes, last season. The temptation is to calculate the damage he could inflict using Costa's soon-to-be-vacated minutes (20 goals in 3,090).
Another way of looking at it might be to say Costa scored 20 goals, despite playing all those minutes. He started 35 games for Chelsea last term and finished 27 of them. Morata completed 90 minutes on just five occasions.
Maybe the reason Morata always looks so fresh and lively is largely because he's always so fresh and lively. Give him a season as Chelsea's first-choice centre-forward and he'll be looking like Kerry Dixon in May. You get easier shifts down the mine.
On that line of thought, perhaps less well-documented than his goal record is how only once in his career has Morata started more than 15 league games in a season. For all his big-game pedigree, it's almost in the humdrum department where he's lacking. Morata is little more than a foal in terms of experiencing the weekly grind endured by a warhorse like Costa. The Premier League striker most likely to pitch up on Game of Thrones wearing just a loincloth, before proclaiming to be the offspring of a dragon and a white witch, is a warrior like few others.
That Morata's latent talent does not marry up with the amount of football he has played is not his fault, nor is it a criticism on this writer's part, but rather a forewarning that to multiply out his goals based on increased anticipated minutes at Chelsea could be the equivalent of expecting Usain Bolt to lap Mo Farah over 5000 metres based on his time over 200m.
What there's no escaping from is that for Morata to get close to matching Costa's usual quota of league goals, he will almost certainly need to start double the amount of the games he has in any previous season in his career.
Though a completely different type of player, Morata has always suffered from the Ole Gunnar Solskjaer syndrome of being so good off the bench that it becomes hard to imagine him as an automatic first choice. It's a niche no player wants.
There has been a fair amount of revisionism over Costa since Conte made clear divorce papers are in the post. For while there's no doubting he can be streaky in his scoring—he netted just three times in Mourinho's annus horribilis prior to the Portuguese's abrupt departure in December 2015 and had a similarly abject barren run in March and April last term—it would be disingenuous to suggest he has been anything other than a magnificent centre-forward for Chelsea.
However much of a pain in the arse he is for his managers, it's nothing compared to the grief he gives opposition centre-halves.
Morata could do worse than ask Costa for a little advice on how to succeed a legend. Perhaps one of Costa's greatest achievements is how Didier Drogba's name can be brought up openly in conversation, without first having to warn those Chelsea supporters of a sensitive disposition to leave the room. Separation anxiety that could have been rife has been conspicuous only in absence.
If Morata can make this latest striker transition at Stamford Bridge as seamless, Chelsea will have bought very well.
With Costa's return to Atletico, perhaps via a sojourn in Milan en route, surely now a question of when not if for a player who will leave the Premier League an eminently duller place in his absence, Chelsea will start the season with a pair of strikers who have just a solitary Premier League start between them.
Michy Batshuayi has earned praise from his manager for a lively pre-season, on the back of an improved end to the previous campaign that saw him score the goal that won Chelsea the title, but the Belgian is a real-life case study on how debut campaigns in England can be tricky.
If that's a bleak prognosis, the antidote is to watch back the 20 goals Morata scored for Madrid last season. It quickly reminds how he is capable of registering all types. At 6'2", it's unsurprising a fair portion come courtesy of his head, but it's a real mixed bag. A couple from distance are the standouts, then there's a pair of solo efforts with searing finales, tap-ins, rebounds, a nutmeg and a first time lob that suggests there might be more to this kid than deadpan finishing. That one was a goal with a wink.
What binds this disparate catalogue of finishes, with either foot and he loves a near-post slot with the eyes, is how effortless and accurate the vast majority are. Very few are scruffy; if he were a decorator, he'd tape everything up before he got started. There is more than a little of the Ruud van Nistelrooy about how un-showy his finishing is. Rarely does he take more than a couple of touches.
He demands the ball to follow the path of least resistance; only occasionally does the goalkeeper get a touch. But when the opportunity arises to stick his boot through it, he's not averse to having the ball kiss the net with all the ferocity of a sailor on shore leave getting reacquainted with a girlfriend.
While tidy and intelligent buildup play has drawn comparisons with Fernando Morientes, how he attacks the ball in the air with real punch and purchase recalls Ronaldo. Eight of his 20 goals last term were headers, compared with just the two Costa managed in the Premier League.
Morata's presence will certainly give Chelsea wing-backs Marcos Alonso and Victor Moses an even more direct outlet to hit through the middle. At times last season the inclination always seemed to be to work the ball back inside.
He's quick too, with his experience of playing wide clearly having benefitted his movement. Though he enjoys operating with his back to goal and linking play centrally between the widths of the goal, his ability to curve his runs from outside in should bring out the best in the likes of Eden Hazard, Willian and Pedro. All of them are capable of dropping a perfectly weighed pass into the peripheral space between a centre-half and his full-back, and that's the area Morata loves to ghost into. Though he lacks the physical strength of Lukaka or Costa, he's technically superior to either of them.
He also seems to be quite the thinker. As a rule, getting footballers to open up is on a par with inducing Mafioso members to do likewise. There's a reason why Johnny Depp's FBI character in Donnie Brasco is undercover and wears a wiretap. Credit then to the always well-informed Lowe for the brilliantly candid interview Morata gave to him earlier in the year.
Reading it feels a little like eavesdropping on a chat between a therapist and his patient. It's a sign of a great interview when it is easy to imagine the subject being reclined on a brown leather couch at the time of interrogation. Think Tony Soprano when he finally starts to spill to his psychiatrist Jennifer Melfi.
It's rare to find any player willing to be candid about the psychological side of football, let alone one of the most expensive in the game's history. Morata with his guard down makes for a fascinating interviewee, coming across as intelligent bordering on melancholic.
He tells a revealing anecdote of how when at Juventus he was ordered home by Gianluigi Buffon, for hard but kind reasons, after he found him in tears on the treatment table.
Clearly a sensitive soul, he comes across less battle-hardened than scarred by the experiences he has been through already. At 24, he is on to his third different league, his third different country. Whereas with most footballers there's a sense they would love nothing more than to stop time at the end, with Morata it seems like it might just come as a relief.
He said: "The good things are incredible, better than you ever imagined – scoring a goal at the Bernabeu, or in the Champions League; the bad are harder. Thirty, 40 years like this and some people would go mad."
He concedes playing for twin European titans Real Madrid and Juventus has not made him immune to what can be the flooding sensation of self-doubt.
On a barren run he endured in his second season in Turin, he told Lowe: "People think we're machines; they don't realise that behind a bad run there's almost always a personal problem, some family issue. You have feelings, you make mistakes, you're a person. I was a bit lost."
Now he's found. With a bit of luck, Chelsea will prove to be the long-term home he seems to have spent most of his career searching for.
If it isn't, and he fails to cope with the pressure of being a No. 1, maybe then the true value of the wholly unique specimen that is Diego Costa will finally be universally recognised.
All statistics in this piece were worked out via WhoScored.com unless where otherwise stated