Milan will qualify for the knockout stage if it wins Wednesday at the San Siro, and the recent praise it has received for its entertaining style of play has been built around the attacking trio of Ronaldinho, Marco Borriello and Alexandre Pato.

"Now, he is very focused and working hard for the team," Leonardo said of Ronaldinho. "He is approaching his best form from the past. Finally, he understands (what he has to do) and has found the right role."

Ronaldinho has been playing on the left wing but often drifts infield to link with Borriello and Pato.

"I feel great and where I'm playing I can do my best," Ronaldinho said. "I'm happy to play behind the strikers, but where I'm playing now is my best position.

Milan has shown its better form away from the San Siro, beating Real Madrid 3-2 in the Spanish capital and Marseille 2-1 in France. At home, Leonardo's side slipped to a shock 1-0 loss to FC Zurich and drew 1-1 with Madrid.

Milan is joint top of Group C, along with Madrid on seven points. Marseille is third with six, three more than Zurich.

"We have to do it," Milan defender Thiago Silva said. "Qualification would help us in the league. It won't be easy, though. Marseille is dangerous in attack."

Leonardo is hoping to welcome back midfielder Mathieu Flamini, who began his career on the south coast of France before moving to Arsenal and then Milan. Borriello is set to undergo a test on a knee injury but is likely to play.

"I twisted my ankle last Wednesday," Flamini said. "I could not play on Sunday and we'll take a test on Tuesday. I will then train with my teammates to see whether I am OK or not. But I'd really love to be present for this game."

Marseille goes into the match off the back of a morale-boosting 1-0 victory against fierce rival Paris Saint-Germain, but it has been a mixed season for Didier Deschamps' side, which is seventh in the league standings.

"We had a good rhythm and pace (against PSG)," midfielder Fabrice Abriel said. "We managed to keep it up in the good parts and bad parts of the match. We protected our goal and looked after the ball and made their players do the running. We should have scored more than the one goal though.

"Milan will play its game no matter what happens and play attacking football. They will try to put us under pressure, play the ball and use their individual skills. We can't fear them, even if we respect them."