Atletico Madrid hold the slight edge over Barcelona going into Wednesday's Champions League quarter-final second leg at the Vicente Calderon thanks to the away goal they claimed in their 1-1 first-leg draw.
Unable to win at the Camp Nou last week, the Catalan giants now face the very real prospect of not reaching the last four of the competition for the first time since 2007, per UEFA.
Diego's stunning strike, shown below, was cancelled out by Neymar, but the away goal could be key for Diego Simeone's side.
However, there is still everything to play for in Madrid, where at least one Spanish side are guaranteed not to be returning for the semi-finals.
Here's how to catch all the action.
When: Wednesday, April 9, at 7:45pm BST/ 2:45pm ET
Where: Vicente Calderon, Madrid, Spain
TV Info: Live on Sky Sports 2/ Sky 1
A succession of draws
These two sides have come up against each other four times so far this season, and there has not been a winner on any of those occasions, with two goalless draws and two 1-1 results, per ESPN FC.
Atletico would be more than happy with a goalless draw, as that would see them through to the last four of the competition, while a repeat of last week's 1-1 would send the tie to extra time.
A score draw any bigger than 1-1 and Barcelona would go through on the away goals rule.
However, Atletico should be confident of restricting Barcelona's goalscoring, as they have the best defensive record in the Champions League so far this season.
They have conceded only five goals from nine games in the competition so far and have not lost a game, while Barcelona have conceded seven and lost once, per Squawka.com.
If Simeone's side can keep a clean sheet, they advance and Barcelona go out. It's as simple as that.
And many are tipping them to reach their first semi-final for 40 years, including football reporter Mina Rzouki:
40 years ago, Atletico Madrid made the semi-finals of the Champions League. I genuinely believe they can do it this year.— Mina Rzouki (@Minarzouki) April 1, 2014
Atleti will be hoping that Diego Costa, who went off in last week's first leg, will return to play some role in Wednesday's match.
The Spanish striker has scored seven goals in six Champions League appearances this season, per Squawka.com, and it would be a huge boost if he were to return for this clash.
Messi's performance holds the key
As ever with Barcelona, it could be the performance of Lionel Messi that determines whether or not they stay in the competition.
He does not have a great record of late against the Madrid outfit, having not scored against them in their last five meetings per Guillem Balague of Sky Sports, but historically he has been lethal against Atletico.
Who will reach the Champions League semi-finals?
According to the Barcelona website, Messi has scored 20 goals against Atleti, and Barca have only lost once to them in a game when the Argentinian has found the net.
The 26-year-old is in impressive scoring form; he has 10 goals in Barca's last five league outings, including a hat-trick against Real Madrid, per BBC Sport.
Atletico currently sit one point clear of Barcelona at the top of the La Liga table. A win for Atletico on Wednesday could galvanise them further in the league, which could be very significant for the rest of the season.
However, if Messi puts in a performance and sees Barcelona through to the semi-finals, Simeone will have to work hard to pick his side up and ensure they see the league title fight through to the end.