Larry Walker, who has strongly hinted at retiring after this season, has fought a herniated disc in his neck throughout the summer. He had a third cortisone shot in July and went on the disabled list for several weeks before returning Aug. 20. When he starts today as planned, it will be the first time since returning that he's started three consecutive days. A fourth cortisone shot is expected to be needed to alleviate the pain for the postseason. The entire year has "been a challenge," Walker said before Friday's game. The most recent challenge has been accepting that he cannot perform at the MVP and batting-champion level of former years. The neck pain is too restrictive, too prohibitive. Too frustrating, as Walker showed right before hitting the homer.