ROME, May 1 (Xinhua) -- AC Milan captain Paolo Maldini will have to sit out the second leg of the Champions League semifinals against Manchester United on Wednesday due to a left knee injury.

"Paolo Maldini will remain in the team's training camp even though he's not available for tomorrow's game," coach Carlo Ancelotti told Milan Channel late Tuesday.

Maldini worsened a knee problem in the first leg last week, which United won 3-2.