Striker Pato faces a race against time to recover from a thigh injury for the first leg of AC Milan's UEFA Champions League round of 16 tie against Arsenal FC on 15 February.
The 22-year-old Brazilian strained his left thigh after scoring the extra-time winner in his side's Coppa Italia round of 16 game against Novara Calcio on Wednesday and, according to his club, will need three or four weeks to recover. Pato was plagued by injuries last season, and was absent for a further seven weeks after suffering another muscular problem in September.
Pato scored twice in three group stage matches this season. The return leg of the Arsenal game will be played in London on 6 March.
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