Headley, on the disabled list since April 25 with a strained right calf, appeared in his first Minor League rehabilitation game on Monday for Class A Advanced Lake Elsinore.
Quentin, after playing in two games over the weekend, was back at Petco Park on Monday to work out with the team. Manager Bud Black said he'll likely rejoin Lake Elsinore on Tuesday, though a very small consideration was being made for him to join Triple-A El Paso in Fresno.
The Padres designated outfielder Xavier Nady for assignment earlier on Monday and recalled outfielder-first baseman Kyle Blanks from El Paso.
Elsewhere, pitcher Casey Kelly, who made his first Minor League rehab start on Saturday for Lake Elsinore, will rejoin that team on Thursday for a start. He'll throw five innings or 75 pitches as he continues to build his endurance and arm strength. Kelly had Tommy John surgery last April.
Kelly threw a bullpen session before Monday's game, with Black and pitching coach Darren Balsley both watching him.