DERBY, England -- U.S. midfielder Eddie Lewis needs a knee operation, ruling him out of next week's exhibition game against Mexico in Houston. "He needs a small operation to remove some cartilage," Derby manager Paul Jewell said Tuesday. "That could keep him out for about a month." The 33-year-old Lewis was injured during Saturday's FA Cup loss against Preston and will be unable to play during the club's first matches under the new American ownership of Detroit-based consortium General Sports and Entertainment. The Rams have won just one of their 23 Premier League matches this season.