Mata said that playing with his compatriot Torres in the team was simply not the same.
"With Fernando it's different. His runs aren't the same. He's not a funnel for our play like Drogba could be.
"He doesn't like the holding-it-up role. He prefers finding space and facing the goal."
He told French magazine So Foot that the £50million price tag was weighing on Torres' head.
Mata explained: "When someone pays that much for you and you become the most expensive player in the Premier League, you are eager to please. Too eager, maybe.
"Especially Fernando, because he's a very humble guy who knows where he comes from and understands the value of money.
"For me, he is still one of the best strikers in the world."