COMMENT: The Catalan coached his boyhood club to the treble in 2009 but just reaching the final with Bayern this season would be more significant

By Peter Staunton Follow @petermstaunton

//There has always been a degree of scepticism about Pep Guardiola's work at Barcelona and now at Bayern; as if he has simply been handed two squads of world-class players and all he has to do is stand on the sidelines and watch them score goals.He has indeed inherited two great teams but nothing in his career so far will have prepared him for what is about to transpire in this upcoming series of games. Guardiola is facing the most intense challenge of his coaching life. Against Barcelona on Wednesday at Camp Nou he will have to demonstrate that his side can legitimately be described as the best in Europe. That is not easy. It is even more difficult when he has only half a team.Not once this season has Guardiola had a full squad available to him. Philipp Lahm and Bastian Schweinsteiger, two World Cup and treble winners, have missed huge chunks of the campaign. Last summer's marquee signing Medhi Benatia has also broken down too often. Franck Ribery remains touch and go for this week but his season, like so many others at Bayern, has been injury-ravaged. Pep has had to do without his two Spanish maestros, Thiago Alcantara and Javi Martinez, for most of the season although their return at this part of the campaign could now prove crucial.While those players have finally regained fitness, other important ones have been struck down. Arjen Robben and David Alaba, the best attacker and best all-round player in the squad respectively, are marked absent until next season. Robert Lewandowski, who has toiled diligently all season while those around him were dropping like flies, is recovering from concussion, a broken nose and a broken jaw. Holger Badstuber was again emerging as a key defender but another muscle injury has stricken him lame.Pep's season has been more about managing resources than implementing the next stage of his grand plan. He has turned up on matchdays with only 14 fit players. No coach can conduct significant work on the training field with those numbers. Bayern play 34 Bundesliga matches a season. Their squad is 25 players strong. Multiply one number by the other and you get 850 individual matchdays. Guardiola's squad between them have missed nearly 200; around a quarter of all games. Think of Bayern's strongest XI; now think how many times Guardiola has been able to use it. Never has a coach had to achieve so much with so few fit players at his disposal.He should be thankful that Manuel Neuer, Jerome Boateng, Dante, Juan Bernat, Xabi Alonso, Mario Gotze, Thomas Muller and Lewandowski have stayed fit for most of the season between them because they form the core of what has become Guardiola's first choice XI. And now he has to prepare them for mighty Barca.Guardiola has worked out a blueprint for success in the Bundesliga. He has also been aided by his rivals' inability to collect three points in places Bayern do every week. His record against the top teams in Germany is not the best around and it is proving difficult to implement his high-wire football in Europe too. He can dominate the league scene through Bayern's inherent superiority but cannot always bring his style to bear in the most demanding matches. That is not down to any tactical inferiority though - it is because he can never pick his preferred team.By Pep's exceedingly high standards Bayern have played well only twice in Europe this season, such have been the impediments; away at Roma and at home against Porto in the last round. Julen Lopetegui exploited weaknesses in the ranks and ponderousness in possession when Porto beat Bayern 3-1 at the Estadio do Dragao, but Guardiola rectified those errors in the second leg.Bayern were forthright in their attacks. They went wide for crosses and found success which proved that Guardiola is not above compromising or at least varying his football in the name of victory. He will likely have to do that against Barcelona too. Pep is asking the walking wounded to beat the team who, on form, are the best in the world.Contrast the fitness picture at the Allianz, where the long-serving club doctor Hans Wilhelm Muller-Wohlfhart has departed due to the pervasiveness of infirmity, with the serenity at Camp Nou. Luis Enrique, the Barca coach, was criticised for his rotation policy earlier in the season and even fell foul of the moods of Lionel Messi, but the decision to rest players and slowly ease Luis Suarez into the picture is now paying dividends at a key time in the season. While the likes of Robben and Alaba are breaking down, Messi, Suarez and Neymar are just getting going.Guardiola and Bayern were hammered 5-0 on aggregate last yearGuardiola has to find the antidote to world football's most electrifying front three while Messi will relish the prospect at getting one-on-one with Dante and Boateng. Guardiola made Messi into the best player in the world once upon a time. He now must work out how to prevent him from having a major impact on this tie.However, whatever knowledge Guardiola had of the inner workings at Barcelona now counts for little. It is a different club to the one he left. Key figures like Carles Puyol, Victor Valdes and Eric Abidal, the very heart and soul of Guardiola's dream team, have departed. Xavi is marginalised. Marc-Andre Ter Stegen, Ivan Rakitic, Neymar and Luis Suarez represent a bold new Barcelona that is a distortion from what was Guardiola's long-term plans.Ludicrously, Guardiola still needs to prove his credentials at Bayern. It is reckoned to be an easy job; the fact that he cannot win a treble is a bete noire. That demonstrates the level of expectation around both Bayern as a club and the man himself. Pep has to accept that the true indicator of his legacy in Bavaria will come in the Champions League. It is where he will be judged.The defeats to Real Madrid last season were the worst of Guardiola's career. This Barcelona side are similar in terms of the star quality of their forwards and their relentlessness in attack. The total failure against Madrid might yet have a bright side; Guardiola can show he has learned the lessons from last season. He can do that against Barcelona and prove he is now a better coach for that chastening experience.The 7-0 aggregate trouncing of Barca by Bayern in the 2013 semis was widely seen as the end of the Catalans' golden age. Jupp Heynckes and his side destroyed Pep's model over those two legs. After a sticky start Luis Enrique has Barca hitting Guardiola-esque highs this season and certain members of the squad will be hungry for vengeance. Bayern are wounded. Barca are remorseless.If Guardiola and Bayern emerge from this tie victorious then it will be the greatest achievement of his coaching career; greater than the treble, greater than the Club World Cup, greater than all those records broken with Barca.