Lionel Messi returned to training for Barcelona on Thursday, six days before his side will take on Bayern Munich in the first leg of their Champions League semifinal.

The four-time Ballon d’Or winner has been the subject of continued attention since injuring his hamstring in the first leg of the Blaugrana’s quarterfinal against Paris Saint-Germain. While Messi came on for the final 30 minutes in the return leg to help see Barcelona progress, he missed the 3-0 victory over Real Zaragoza on Sunday.

But, in a statement on their Web site, the Liga leaders revealed that Messi was stepping up his recovery.

“The big news at today’s training session was the presence of Leo Messi,” read the statement. “The Argentinian, who injured his right hamstring at the Parc des Princes, started doing fitness work on one of the Ciutat Esportiva fields.”

While Messi moved from the gym onto the training pitch, he still wasn’t taking full part in training and there must be some doubt whether the player will be at full fitness to take on Bayern Munich in the Allianz Arena next week.

What is also apparent, though, is that the influence of even a barely half-fit Messi on Barcelona can be enormous, perhaps too big.

The fact that Messi has not even been training since shows how important Messi is to Barcelona, even by including him on the bench against PSG, never mind bringing him on for half an hour.

Yet, what cannot be argued is that the move paid dividends.

Without Messi, Tito Vilanova’s side were looking set for a shock exit from the Champions League as they trailed PSG at home and were devoid of their attacking rhythm, while the Ligue 1 leaders took the game to Barcelona at Camp Nou like few sides have since their dominance began under Pep Guardiola in 2008.

Simply Messi arriving on the pitch not only changed his own side’s mentality but also that of the opposition. The 25-year-old played a key role in the goal that took Barcelona through, but it was the intangible elements that were most important on that night.

That a team which featured a host of World Cup winners should be so dependent on one man is a little perverse.

In some ways it is by design in that all Barcelona’s attacking play goes through him; not a bad idea when you have a player who could well go down as the greatest in history.

Such focus around one man does have its problems, though. For one, it has meant that quality forwards who have been brought in alongside Messi -- namely Zlatan Ibrahimovic, David Villa and even Alexis Sanchez -- have never truly reproduced their form elsewhere with the diminutive magician around.

Even with Messi in the side, Barcelona have not looked as incisive in the final third of late as they have in the past, particularly in games against Milan and Real Madrid. That there has been so much reliance on Messi and that Villa, Sanchez and Pedro have all had their struggles during the campaign has allowed defenses to crowd out Barcelona’s star man.

They have taken the breath away in patches against Milan and PSG, but against Bayern Munich Barcelona will experience a significant step up in quality.

In what was expected to be a closely-fought contest in the quarterfinals against Juventus, Bayern brushed the Italian champions aside, 4-0 on aggregate. And in the past three weeks domestically, Jupp Heynckes’ men have won matches by scores of 9-2, 4-0 and 6-1 and that when they weren’t even at full strength.

Perhaps most enticing about a mouth-watering semifinal is that it is a contest that will pit arguably Europe’s two finest midfields against each other.

Crucial to establishing Barcelona’s passing rhythm is Sergio Busquets and, like Messi, the defensive midfielder also returned to training on Thursday as he recovers from a hernia.

Bayern have no such hope of a return for one of their midfielders with Toni Kroos expected to miss the rest of the season with a groin injury. It is a huge blow for the Bavarians, with the 23-year-old having become increasingly influential as the most advanced of their trio of midfielders. His ability to combine quality passing, forward runs and defensive responsibility made him the key player in Bayern’s victory over Real Madrid in last season’s Champions League semifinal.

Although they don’t have a like-for-like replacement, Bayern do have a squad packed deep with quality and Messi and Barcelona are likely to have to be at their best to prevent the Bundesliga champions from claiming a spot in the Champions League final for a second straight year.