The Germany international has been out injured for seven months and undergone two operations on his ankle but was watched by manager Avram Grant against Birmingham's second string at Brentford last night.
The 31-year-old came off at half-time and will resume training with the first team on Thursday after they have returned from the Champions League trip to Rosenborg.
"It's my first 45 minutes for a long time," Ballack told Chelsea TV. "I feel good. It's a long time to wait because of injury so I am happy to be back.
"You are a little bit careful. I'll train next week and see how it is, then maybe have another game in the reserves.
"I'm looking forward to playing in the first team."