Cech believes Spaniard De Gea is getting to grips with the Premier League after some early errors, the Chelsea keeper admits his team will 'try to test him' at Old Trafford.
Cech said: "You can see the difference between being a keeper here and in La Liga - in particular, in the game at West Brom the surprise on his face at how difficult and physical it is to go out and catch a cross. He's learning fast. You can't say he is United's weakness.
"At 1-0 against Arsenal he saved a penalty that changed the game. Then they scored eight goals and without that save it could have been a different story.
"And against Bolton he made a good save from Martin Petrov, so every game he is improving."