The treble is the ultimate prize in club football, an achievement that sees a team win the league, the premier domestic knock-out competition and the European Cup.
The feat is near impossible, and rarely achieved.
Celtic did it in 1967, Manchester United in 1999 and remarkably it's been accomplished twice in recent years after Pep Guardiola guided Barcelona to the treble in 2009 and Jose Mourinho won three trophies in his final year at Inter Milan in 2010.
Eight teams in this year's Champions League are still in a position to complete the treble - but only one can possibly do it.
Here, we take a look at those still in the hunt and assess their chances...
In the quarter-finals of the FA Cup - play Chelsea or Middlebrough
12 points clear in the Premier League
Drawing 1-1 with Real Madrid after first leg of last-16 tie
One thing in Sir Alex Ferguson's favour is he knows how to go about it. Manchester United's experience from 1999 will tell him that it won't be easy, and their hopes will hinge on pivotal moments such as Ryan Giggs' wonder goal against Arsenal in the FA Cup and unbelievable comebacks against Juventus and Bayern Munich in the Champions League.
Currently 12 points clear, it seems impossible they can throw away the Premier League. The cups may not be so straight forward. A potential FA Cup meeting with Chelsea awaits and then there's the small task of navigating their way past Real Madrid in the Champions League. As Jose Mourinho said in the aftermath of the first leg - it's 50-50.
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In the quarter-finals of the Scottish Cup - play St Mirren
19 points clear in Scottish Premier League
Trailing 3-0 against Juventus after first leg of last-16 tie
On the domestic front, Celtic are looking good. The absence of Rangers has seen them dominate the Scottish Premier League like never before. But any hopes of repeating their treble exploits of 1967 were almost certainly dashed when Juventus punished them at Celtic Park with three away goals.
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In the semi-final of the Copa del Rey - tied 1-1 with Barcelona after first leg
16 points behind La Liga leaders Barcelona
Drawing 1-1 with Manchester United after first leg of last-16 tie
Jose Mourinho completed the treble with Inter Milan three years ago in what was his final season at the Italian club. His chances of repeating the feat in what appears to be his final year at Real Madrid look slim. His side's chances of beating Manchester United at Old Trafford in the Champions League are no better than 50-50, and the same could be said about progress in the Copa del Rey against Barcelona. But it is in the league where things fall down. Currently third and trailing Barcelona by 16 points is surely too big a margin to make up.
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In the semi-final of the Copa del Rey - tied 1-1 with Real Madrid after first leg
12 points clear in La Liga
Trailing 2-0 against AC Milan after first leg of last-16 tie
Before they even made it to this stage, Barcelona would have been the favourites to be fighting on all three fronts come the business end of the season. And up until last night few would have doubted their chances of repeating their achievements of 2009. Well clear in the league and one game away from the Copa del Rey final, things are looking good on the domestic front. But a shock 2-0 defeat to AC Milan leaves their Champions League hopes hanging by a thread. While a team comprising Lionel Messi, Andres Iniesta and Xavi can never be discounted - one goal for AC Milan at the Nou Camp will leave Barca needing four. Even for them that's a tall order.
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In the quarter finals of the Ukrainian Cup - play Karpaty
13 points clear in the Ukraine Premier League
Drawing 2-2 with Borussia Dortmund after first leg of last-16 tie
Shakhtar Donetsk dominate all before them on the domestic front and have won the league for the past three seasons. Currently 13 points clear, making it four should be a formality. They've won the domestic cup for the past two seasons as well and remain in the hunt for a third in a row. It is in the Champions League that the Brazilian infused side will have their greatest task. After drawing 2-2 with Borussia Dortmund in the first leg of their last-16 tie a quarter final place is a real possibility, but those away goals for the German side could count against them.
Chances of the treble: Domestic bliss, but European botheration
In the quarter-finals of the DFB Pokal - play Bayern Munich
13 points behind Bundesliga leaders Bayern Munich
Drawing 2-2 with Shakhtar Donetsk after first leg of last-16 tie
After back-to-back Bundesliga titles, Borussia Dortmund are at real risk of losing their domestic crown. And it is Bayern Munich who hold their fate in their hands. Dortmund will have to reign in a gap of 13 points in the league with just 12 games remaining. Jurgen Klopp's side must also muscle their way past Bayern in the DFB Pokal. Perhaps it is the Champions League in which they have their best chance of success. With the likes of Robert Lewandowski, Mario Gotze and Marcos Reus among their ranks, they'll be a match for anyone, as long as they can complete the task against Donetsk and reach the last-eight.
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In the quarter-finals of the DFB Pokal - play Borussia Dortmund
13 points clear in the Bundesliga
Leading 3-1 against Arsenal after first leg of last-16 tie
The performance against Arsenal in midweek spelled out (if anyone wasn't already aware) that Bayern Munich are among the best teams in Europe. Their fluid, incisive play tore the Gunners apart and a place in the quarter-finals is all but guaranteed. Having made the final in two of the last three seasons, few should doubt their Champions League credentials. And this season, they're performing at home as well. A huge lead in the Bundesliga should see them regain the title from Borussia Dortmund before Pep Guardiola arrives in the summer. Last year they blew it in the finals of the DFB Pokal and Champions League, can they make amends?
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In the last-16 of the Coupe de France - play Marseille
3 points clear in Ligue 1
Leading 2-1 against Valencia after first leg of last-16 tie
Perhaps the dark horses for the treble are PSG. The recently mega-rich side have adapted to European football much quicker than their fellow nouveau riche clubs and a place in the quarter-finals of the Champions League look likely after they beat Valencia in Spain. The red card for Zlatan Ibrahimovic has put a spanner in the works, but they should be turning out among the last-eight. Carlo Ancelloti has taken them to the top of the league in France but it remains incredibly tight, with both Lyon and Marseille still in the reckoning. The latter also present a very tough last-16 tie in the Coupe de France.
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