Pompey boss Harry Redknapp will not completely rule out a move.
"Fulham have made an offer for Matty but, at the moment, I don't really want to to let him go," he told Sky Sports News.
"He's a good player and, at the moment, I'm not overloaded on the left side. I'd like to keep him so, at the moment, there's no deal.
"You never know. I'd like to try and balance the books a little bit."