FC Barcelona plays perhaps the most important game of the season to date when Inter Milan visits the Camp Nou Stadium on Tuesday night.

Barcelona goes into the match third in its qualifying group and knowing that defeat to the side coached by Jose Mourinho could leave them out of the competition they won last June.

Barcelona coach Pep Guardiola has to count on several injury worries. Star striker Leo Messi limped out of Saturday's 1-1 draw in Bilbao with a groin strain.

Medical reports on Sunday gave him a chance of playing, but Messi will be a doubt until the last moment and could well start the game on the substitutes' bench.

Zlatan Ibrahimovich is also doubtful for the match against his former side after missing Saturday's match with a hamstring problem, while Rafael Marquez has a fever and Toure Yaya and Eric Adidal have cases of the A/H1N1 Swine Flu virus.

That means Maxwell will play at left back with Carles Puyol and Gerard Pique in central defense and Dani Alves on the right.

The Barca defense will have to be at its best, because former Camp Nou hero Samuel Eto'o will be doing his best to score against his former club.

Eto'o, who scored the opening goal of last season's final, was deemed surplus to requirements by Guardiola and formed part of the Ibrahimovich transfer.

He will be keen to show Guardiola was wrong and his pace will be a constant threat.

The Camp Nou will also be looking forward to welcoming back Mourinho, who was assistant to Bobby Robson in the late 90s. Mourinho became a hate figure for the Barca faithful during his time at Chelsea and can expect a difficult evening.

With the visit of Real Madrid around the corner, Barcelona needs a win both to boost club morale and also to ensure its place in Europe. Any other result would be seen as a humiliation before the month of November has finished.