Cincinnati Reds outfielder Ken Griffey Jr. will undergo surgery on Monday to clean out both his left knee and the scar tissue surrounding the incision where he had right hamstring surgery last season and will be sidelined for the remainder of this year. Griffey, who has not played since September 4 because of a sprained right foot, is one of the prime candidates for the National League Comeback Player of the Year award after hitting .301 with 35 homers and 92 RBI in 128 games this season for the Reds. His 536 career home runs are tied with Mickey Mantle for 12th on the all-time list. The 35-year-old Griffey has been injured in each of his last four seasons with the Reds and has already had several surgical procedures since joining the club before the 2000 season. Cincinnati has been out of playoff contention for sometime and at 70-81 is 25 games back of the St. Louis Cardinals in the National League Central.