Headley, regarded as the Padres' top Minor League prospect, hasn't officially been added to the Padres' roster and won't be until Tuesday, when San Diego opens a three-game set against New York at Yankee Stadium.
But Headley was summoned from Triple-A Portland on Saturday and arrived late after a flight from Fresno, where the Beavers were playing.
San Diego manager Bud Black said Headley will travel with the team to the Hall of Fame Game on Monday in Cooperstown N.Y., and will get some at-bats in the game against the Chicago Cubs before the series against the Yankees.
Headley, the converted third baseman who is in his first season playing the outfield, was hitting .305 with 13 home runs and 40 RBIs in 65 games for Triple-A Portland.
This isn't his first turn with the Padres, as he appeared with the team twice last season in Chicago when third baseman Kevin Kouzmanoff came down with a tight back and later when the rosters expanded after Sept. 1.
"Obviously last year, getting that first time out of the way and the initial jitters out of the way was big," Headley said. "This time, I had camp [Spring Training] with all the guys. I think I'm a lot more comfortable now than I was last year. Hopefully, I'll use that experience from last year and this spring to move forward the best I can."
This time, the expectation level is different, as Headley is expected to play nearly every day, mostly in left field, though he'll give Kouzmanoff -- who has missed just one game this season -- occasional relief at third base, his original position.
"They just told me that every now and then I might be in at third to give Kouz a day off ... they want me to stay sharp there," Headley said. "But from my understanding, it's going to be a majority of the time in left."
This season, Headley, a switch-hitter, bounced back after a slow start to the season (.242 batting average in April) by hitting .357 in May. He cut down on his strikeouts, hit with more power and took more walks, which more or less matched his professional profile.
"I made some adjustments at the plate. In Triple-A, there [is] a lot more experience; guys know what they're doing a little bit more," Headley said. "I was seeing more off-speed [pitches] than I was before. It took me a little bit to make the adjustment to that, but once I figured out my approach, I got back to where I needed to be."
The Padres balked at promoting Headley sooner than now for a myriad of reasons. They wanted to see him have more success in Portland and wanted to see him continue to play the outfield to get acclimated to a new position.
And, as general manager Kevin Towers said repeatedly, he wanted to bring him up at a time when the team was doing better so that Headley wasn't seen as a savior of sorts. Now is that time.
"I think the environment is much better than it was three weeks ago," Towers said. "We have got a lot of guys contributing offensively. When he gets here, he shouldn't have to feel like he's got to carry this ballclub. We're playing good baseball now.
"To me, now is kind of the right time to have him here, when things are going well."
Headley admitted to being excited about the prospect of making his season debut with the Padres at Yankee Stadium.
"When the schedule came out ... that's a series I don't want to miss. What better place to start? I started in Wrigley [Field] last year, so I guess I'm 2-for-2."
Corey Brock is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.