EDMOND, Okla. (AP) -- Larry Mize withdrew from the U.S. Senior Open on Sunday because of a back injury.
The tournament starts Thursday at Oak Tree National.
Mize, the 1987 Masters champion, was replaced by Daniel Koesters of Las Cruces, New Mexico. Koesters was the first alternate from the Albuquerque, New Mexico, sectional qualifier.
Also Sunday, Ken Martin was added to the field.