Roberto Martinez has claimed that defender John Stones underlined his importance to Everton in Saturday's 3-1 win over Chelsea at Goodison Park.
The 21-year-old was heavily linked with a move to the Premier League champions in August, and posted a transfer request which was immediately rejected.
Nevertheless, Stones played on despite the speculation and starred against the Blues yesterday, and the Toffees boss claims that he consolidated his 'irreplaceable' status.
"Sometimes you play against the champions and you can beat them, but you look at lucky breaks - but for 90 minutes we restricted Chelsea to two shots on target," he is quoted as saying by Sky Sports News.
"Clearly John showed we couldn't replace a player like John Stones at that stage.
"He has been heavily tested but we never had a doubt in the way he would perform and he never let the team down."
Two goals from Steven Naismith helped the Toffees into a 2-0 lead, with Nemanja Matic pulling one back before the break, but the Scottish midfielder completed his hat-trick in the second half.
