"You look at Steven and what he has done for us this season, to have scored 17 goals for Liverpool, that is just fantastic," he said.
"I don't know how important Lampard is for Mourinho, but Gerrard is the key for us. People compare the two players and they say that Lampard scores more goals and he plays more games.
"But to score 17 goals for a team like Liverpool that scores far less than Chelsea, that shows Gerrard really is the key player.
"Lampard is a very good player but he has very many good players - very expensive players - around him at all times.
"Sometimes Chelsea have such dominance that they can coast through games - they find it easier at times to win matches.
"So people say that Lampard plays so many games, but when you are winning two or three-nil with plenty of time to go, then it is easier to manage that game, to rest in the contest.
"We don't have that luxury and it means our players get harder matches. Gerrard has to play hard through many matches but he is still offering so much to us every game."