Efrem Lukatsky/Associated Press

He's arguably been Bayern Munich's second-best and most consistent player this season behind Arjen Robben. Yet if the Munich giants are to win the Champions League, Pep Guardiola may need to drop Xabi Alonso.

It may seem paradoxical, but the Champions League is an altogether different game than domestic league football. There are no easy opponents in the knockout rounds, and players enter every match knowing it is the biggest test of the season until then. Unfavored teams don't rotate to rest players in expectation of a loss, nor do they simply give up after conceding once or twice.

Tactically, coaches have to be much more careful and conservative, knowing that just one goal conceded could erase months of hard work. Yet they must find a balance and the best possible formula for success, given that opponents will have spent weeks studying their strengths and weaknesses. It's football at the highest level.

If there's any doubt as to the difference between domestic and league play, consider that Bayern beat Hamburg and Paderborn by a combined 14-0 in their last two Bundesliga matches. Between those fixtures, they played an entirely beatable Shakhtar Donetsk in the Champions League round of 16. Despite facing opponents who were still on winter break and were playing further from home than Munich, the Germans were held to a scoreless draw in which they took just five shots.

In L'viv, where Shakhtar play home games due to the war in Ukraine's east (they currently train in Kyiv), Bayern were let down by a pair of rash challenges by Alonso, who was sent off with 25 minutes left to play. Even at 11 vs. 11, Bayern had plenty of time but struggled to break down the Shakhtar defense.

Bayern's lack of fluency going forward in that game stems from the combination of Alonso and Bastian Schweinsteiger being used in central midfield. Despite Guardiola's insistence that they can operate together (the trainer said in December that they could, opining in a press conference, per German magazine Kicker, that the German offers more attacking qualities), evidence thus far has suggested otherwise.

Bayern looked stale in the first half but eventually beat Augsburg by a convincing 4-0 margin in Schweinsteiger and Alonso's first appearance together in December. Since then, the pair have started four games together, of which Bayern have won just one. Although facing rather weak opposition, it may be no coincidence that the Hamburg and Paderborn results were earned using only one of the clashing pair in the starting lineup.

Former Bayern captain and Sky pundit Stefan Effenberg recently made a sharp analysis of the Schweinsteiger/Alonso pairing, as quoted by German Fussball-Vorot.de. The retired midfielder claimed that the two are excellent players who would start at almost any club, but are too similar and slow on and off the ball. He signified that although they are a passable combination in some games, their clashing styles can be a problem when it comes to facing Real Madrid, Barcelona and other elite clubs.

Actually, Effenberg perhaps overplayed Alonso and Schweinsteiger's effectiveness. The one game Bayern have won with the duo in 2015 was against relegation candidates Stuttgart. The two draws came against Schalke and Shakhtar, teams well below the standard of Spanish giants Real and Barca. And against Wolfsburg, also a side that aren't exactly at the pinnacle of Europe, Bayern were hammered 4-1.

In Wolfsburg, Bayern were brutally hacked apart on the counterattack, their holding midfield pair lacking the pace to close down space and track the likes of Kevin de Bruyne and Maximilian Arnold as they counterattacked through the center. Against Shakhtar, Bayern didn't concede. But again, Schweinsteiger and Alonso's lack of pace were exposed as they were forced to hack down their quicker opponents, accumulating three yellow cards between them. One can consider how such tactics would have fared against Real Madrid and only cringe.

In L'viv, Schweinsteiger's limited ability going forward was also exposed as Bayern hardly had a chance to score. Yes, Guardiola should also be faulted for keeping Robert Lewandowski on the bench, but it's no mystery that his vice-captain is no Toni Kroos or Thiago Alcantara. He spent the first half of his career a mediocre attacking player before becoming world-class when Guardiola mentor Louis van Gaal transformed him into a holding midfielder in 2009.

Having established that the Schweinsteiger/Alonso combination is not the way forward for Bayern, the question naturally arises: Who should start?

In his interview, Effenberg asserted that a fully fit Schweinsteiger will likely be hard for Alonso to displace. On the other hand, readers of Pep Confidential, Spanish journalist Marti Perarnau's insider-look at Guardiola's first season in Munich, will be aware that the trainer has his doubts over the 30-year-old's fit in his game plan.

A recent quote from Guardiola, however, reveals exactly why he needs to trust Schweinsteiger over Alonso. In a Friday press conference (per Goal), the trainer defended his possession-based game and highlighted Alonso's weakness:

"We want to keep the ball with us for as long as we can," he said. "So that's why I want players like Xabi and Thiago.

"But when it comes to running after another player, Xabi Alonso is the worst player in the world! But then, that is not what we signed him for."

True, Bayern signed Alonso for his ability to control games. However, no team in a big test can afford to have a player in a defensive position who struggles to defend. As Matt Whitehouse brilliantly explains in his book, Universality, the time of the midfield specialist (think: Claude Makelele or Juan Roman Riquelme) is gone. Midfielders, strikers and even defenders need a range of useful qualities. If they lack versatility, their weaknesses will be ruthlessly attacked when tested at the highest level.

As a Real Madrid player, Alonso often struggled against pressing German teams. His side were knocked out of the Champions League by Bayern in 2012 and finished behind Dortmund in their group in the fall of 2012 before being eliminated by the Ruhr side a few months later.

Alonso was never the most mobile and best defensive player, and now 33 years of age, he's even less so. Guardiola may be able to mask his deficiencies in the Bundesliga, but he will fail in the Champions League. His costly mistake against Manchester City and sending off against Shakhtar are clear evidence. And he's not the only aging central midfield star to struggle on the greatest stage.

At 35, Andrea Pirlo continues to dominate opponents in Serie A. Yet his Juventus were eliminated from the Champions League group stage a year ago and barely edged Olympiakos to second in their group in the current campaign.

Xavi at Barcelona began to decline a few years ago, his inability to track Ramires' runs in the 2012 Champions League semifinals clearly indicating his downturn. The Catalan maestro has been effective in league play since then, but struggled against physical Paris Saint-Germain and Bayern in the 2013 Champions League, and Atletico a year later. This season he's played in all but five La Liga games for which he was fit, but started just two and gone the full 90 minutes in only one Champions League match.

If Guardiola intends to try to control matches to the point that opponents haven't a chance to make Alonso defend, he's taking the same path that led to Van Gaal's sacking in 2011. Under the Dutch trainer, Bayern's only defense was possession. And although they often scored, they were also too easily torn apart. In the Champions League they were eliminated by an Inter side in the round of 16 that weeks later would be hammered 7-3 on aggregate by Schalke.

To maintain possession and keep control, Van Gaal's Bayern played a dangerously high defensive line. Guardiola's team didn't always do the same, but since the winter break have resorted to old ways. Their offside "trap" against Wolfsburg was so high that their defenders were all 10 or more yards into their attacking half when possession was lost leading to the hosts' third goal. Three of the goals conceded in that match, as well as Schalke's penalty, can be attributed to a defensive line being far too high as Bayern's back four were forced to defend facing their own goal.

Rather than modifying his tactics to mask Alonso's weaknesses, Guardiola would be wise to place his faith in Schweinsteiger. The vice-captain isn't the fastest player and lacks Alonso's passing accuracy, but he is a much more rounded player than the Spaniard and his complete skill set will be harder to exploit.

Despite his recent injuries, Schweinsteiger is three years younger than Alonso and is still in his natural athletic prime. And he proved last summer in Brazil that he still has the fight and grit to doggedly defend.

Critically, using Schweinsteiger in midfield allows Bayern to play a less suicidally high offside trap, provided he has the right partner. To this end, David Alaba is a perfect complement. The Austria international is comfortable on the ball but fully adept playing without it. He has blistering pace and lightning-quick acceleration, and can close down space like none other among Bayern's midfield options.

There are others possibilities, but Javi Martinez has missed the entire season and was previously seen by Guardiola as a center-back, while Thiago will have missed an entire year when he returns in March and is unlikely to reach the form and fitness to start in the biggest games before season's end. Philipp Lahm is also a candidate, but he's more likely to take Rafinha's role at wing-back than to move back into midfield.

It may be true that Schweinsteiger hasn't been at his best for a prolonged period since 2010, a string of injuries having taken their toll. He has, however, achieved a pair of enormous successes since May of 2013, winning the Champions League and World Cup finals.

Although injuries and some disappointments in 2012 may have temporarily marred his reputation in big games, it seems Schweinsteiger's confidence is back and that he's worthy of his label as a leader of the team. At the very least, it's better to hope that the 30-year-old reaches his best form than to settle for Alonso at his peak when it severely strains Bayern's system and makes winning the Champions League an even more difficult task.

On Saturday, Guardiola opted against the Schweinsteiger/Alonso partnership but dropped the former to bring in Alaba. Due to Alonso's sending off in L'viv and subsequent suspension, however, Guardiola will have to drop his compatriot for the return leg. Therein, we'll see how ready the likes of Schweinsteiger and company are to take on Europe's greatest.

@Mr_Bundesliga