Midfielder Osman has been a vital part of Everton's recent great run

Osman, 26, played in Saturday's Premier League win at Upton Park but was in pain and a scan revealed the full extent of his problem.

"It's an absolutely terrible blow," boss David Moyes told the club website.

"He broke his toe in the first five minutes of the cup game but battled on and it shows you how tough he is. He was in a bad way but wanted to play."

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Moyes added: "He had a scan and it showed a big crack and we think he is going to be out for between four to six weeks.

"Leon's form had been good and he has been playing a big part in everything that we have achieved recently."