The Brazilian played the full game as Milan got their second group stage campaign off to a winning start on Tuesday, Andriy Shevchenko scoring the only goal against the defending champions, but a subsequent scan revealed damage to his thigh which will sideline the 30-year-old for two to three weeks.
Rivaldo will definitely sit out the Serie A visit to Empoli FC and the first leg of the Coppa Italia meeting with Ancona Calcio, while the 11 December trip to the Westfalenstadion to face a Dortmund side who also won their opening Group C fixture - 2-1 away to FC Lokomotiv Moskva - could come too soon.
World Cup showdown
If Rivaldo fails to recover he will be denied the opportunity to pit his wits once more against Dortmund's German international duo Christoph Metzelder and Torsten Frings after the trio all featured in the summer's FIFA World Cup final, Brazil defeating their European opponents 2-0.
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