The Mexican, known around Old Trafford as Chicharito, scored 20 goals in his debut season and marked his first start this campaign with two at Bolton Wanderers.
"I am ready," he warned Chelsea, having scored the important goal against them after 35 seconds at Old Trafford last May that effectively sealed United's record 19th title.
"I've done all the work I needed to do and I now feel fit and sharp. My goal against Chelsea last season was vital because it came so early that it helped us win. But any goal is important to me. And playing with Wayne (Rooney) is unbelievable; he can do anything on the pitch."