The striker, who has 15 goals in the Premier League this season, is also a doubt for the second leg of the team's Champions League quarter-final against Bayern Munich next week.
Manager David Moyes told the club's Twitter feed: "He's got a terrible toe. Not only is it a problem for this game, it could be a problem for the Munich match.
"We need to monitor it. We'll get him treatment all over the weekend and see if we can speed it up."