Headley, who missed the first 14 games of the season with a broken left thumb, was activated from the DL and batted third in the series finale against the Los Angeles Dodgers.
Headley was injured sliding into second base trying to break up a double play in a spring training game March 17. He played four games for Class-A Lake Elsinore during his rehabilitation assignment, going 3 for 12 (.250) with a double and two strikeouts.
The 28-year-old Headley had a breakout season last year, hitting 31 homers with an NL-best 115 RBIs while winning his first Gold Glove and Silver Slugger awards. He and the Padres agreed to an $8,575,000, one-year contract in the offseason, avoiding arbitration.
Maybin was put on the 15-day disabled list retroactive to April 16. He is batting .091 (3 for 33) with one RBI and three runs scored in 10 games.