Cardinal slugger Mark McGwire said he would only have surgery on his bad knee as a last resort. Doctors convinced him that was the way to go, and McGwire had surgery over the weekend to repair his right knee. The doctors removed the damaged portion of McGwire’s patellar tendon, and they think he should be ready to play by spring training, though he won’t be 100 percent. McGwire had the surgery in St. Louis, then returned to California, where he will rehab the knee this offseason.Two Cardinal pitchers face offseason surgery as well. Andy Benes will have arthroscopic surgery on his knee, and Jason Christiansen will have his rotator cuff scoped.