The veteran midfielder is in talks with the Blues about a contract extension, with his current deal ending in the summer, but Di Matteo says he is none the wiser as to how things are progressing.
"Ultimately that's between the player and the club to agree a new arrangement,” said the Italian.
"I'm not aware how the discussions are going at the moment.
"If there's a willingness from both sides, he will remain with us.
"He's been a fantastic player for us over a decade, so it would be nice for him to finish his career here."