Dietmar Hamann has signed a new one-year deal at Manchester City.

The former Liverpool and Germany midfielder joined City last summer but struggled with injuries during his first months at the club. However, the 34-year-old has been in impressive form under Sven-Goran Eriksson and was the man of the match in the derby win over Manchester United on Sunday.

Meanwhile, Eriksson is hopeful midfielder Michael Johnson will be fit for their next match against Everton on February 25. The 19-year-old played a major part in City's excellent start to the season but has been out of action since December with an abdominal injury.

Johnson played in a reserve team match on Monday, and Eriksson said: "Michael did very well for 45 minutes, and the positive is that he had no discomfort afterwards. I hope he has no setbacks, and if things go as I think he would be ready for Everton."

Valeri Bojinov, their Bulgarian striker, is not expected to feature against Everton despite a goalscoring return in the reserves draw with Newcastle United. The 21-year-old injured knee ligaments on his first start for City in August and Eriksson does not want to rush him back.

"Bojinov is not ready for the first team yet," he said. "It's like having a new signing but I doubt very much that he would be ready for Everton. But he's got a big smile on his face now, he's very happy."