After a decade of starting in the major leagues, the 39-year-old right-hander made his debut as a Padres reliever Wednesday night, pitching a scoreless seventh against the Giants.
Williams had made a relief appearance with the Cardinals in 2003. And he has pitched in relief in spring training.
"But this was different," said Williams of his new -- and he hopes temporary -- role in the Padres bullpen. "In spring, you're putting in work. You know innings in advance that you're going to work. And with the Cardinals, I knew I was going to work a specific inning to get in a little work.
"But this is different. I have to learn a completely new job -- a new way of getting ready. I'm too old to be learning something new."
Williams and Chan Ho Park were dispatched to the Padres bullpen during the last week of spring training when manager Bruce Bochy decided Dewon Brazelton would be his No. 4 starter. The Padres won't need a fifth starter until around April 10, when either Williams or Park will get the call.
If he remains in the Padres bullpen, relieving will be a blow to Williams' wallet as well as ego. He has more than $500,000 in incentives based on the number of starts he makes.