The two teams meet this weekend in the Champions League final.
"The change of manager this season looks to have brought them closer together," Heynckes told the Daily Mail. "This is the last chance for Frank Lampard, John Terry, Didier Drogba and Petr Cech to win the Champions League together, but Di Matteo still deserves credit for the way they are now playing as a team.
"Experience plays a big part, when you are looking for a manager, but I am very impressed by the way Di Matteo walks beside the pitch. He is very relaxed and seems to be in control.
"That transmits itself to his team. It tells them they are all in it as a unit, sharing one goal. That is the psychological feeling he has achieved at Chelsea.
"People responsible at the club have to decide if he is the right person. It is very difficult to judge that from the outside, but the philosophy has definitely changed in the last weeks."