A player returning from injury can transform an entire side.
In 2004, Arjen Robben suffered a pre-season injury which kept him out of the Chelsea team until late October.
Before his return to fitness, the Blues had secured four 1-0 wins, a 2-0, a 2-1, two goalless draws and their last result was a 1-0 defeat by Manchester City.
Robben came off the bench in the next game, a 4-0 win against Blackburn Rovers.
In the club’s next eight matches, they hit four goals five times. The change was quite astonishing.
Robben bagged four of those goals and set up more for his team-mates.
The Dutchman terrified defenders, giving them something different to think about, something a little bit special.
A decade on, and Neymar will be looking to make a similar impact.
He is a wonderful talent and one which is difficult for other teams to handle, particularly when Lionel Messi is lurking too.
When the Argentine is Barcelona’s main threat, teams often attempt to shackle him directly, using several players to try and stop him.
It doesn’t always work of course, but it usually ensures that instead of running the game he is more limited to making a few key contributions.
Alexis Sanchez and Pedro, fine players though they are, don’t possess the same menace as Neymar.
The Brazilian’s return could have three effects on Barcelona.
Firstly, if Messi is still the centre of attention, Neymar may find more freedom than is wise for him to be allowed.
Secondly, if teams try to deal with his threat adequately, it means his South American co-conspirator will be able to make more of an impact.
The third is psychological.
Barcelona have been suffering recently, on and off the pitch.
Results haven’t been the best—although they have reached the Copa del Rey final and are still top of La Liga—and all the talk away from the football itself has been about Neymar’s transfer.
That is a contentious issue and one which is yet to be resolved.
We’ve seen former Barcelona president Sandro Rosell resign amid allegations about the fee for the Brazilian, which at the moment the club insist stands at €57.1 million.
After quitting, he said, as reported by the BBC: "From the beginning, I have said the signing of Neymar has been correct and his signing has caused despair and envy in some of our adversaries."
But, after being suspended for a match, suffering from gastroenteritis and then spraining his ankle in a Copa del Rey clash against Getafe, he has missed seven games.
The only headlines he has been making are related to his transfer.
But Saturday’s clash against Rayo Vallecano at the Nou Camp could be Neymar’s time to make an impact.
He is likely to start on the bench for that game, having been training with the squad for the last few days.
Neymar was actually called up in the squad for Barcelona’s Copa del Rey semi-final second leg against Real Sociedad on Wednesday night, even though the doctors hadn’t given him the all-clear.
Martino had explained that and more in a press conference before the game, reported by the Daily Mail:
As I have said before, for me if there is a very important match coming up that everyone is talking about, his presence or otherwise does not have the Manchester match as the target. It could be before, it could be after. In any case, it will be when we consider it to be the right time and when we are taking the least risk with the player's future.
The Champions League last-16 tie with Manchester City is the pick of the round and the most interesting match.
Barcelona are weaker than they have been for some time and City the opposite—should Sergio Aguero and Fernandinho be fit to play.
One advantage the Catalans hold over their opponents is big-game knowledge. The Champions League is still a relatively new experience for City.
And if Neymar is ready to play, he may be able to dazzle them in a way that Sanchez, Pedro and Cristian Tello cannot.