It was only the second loss for the Tigers in their last 10 games.
Placido Polanco tied the game for Detroit at 2-2 in the eighth inning with a solo homer, but the Padres broke open the contest in the bottom half of the inning.
Casey Fossum relieved Rodney and walked Brian Giles to load the bases.
Adrian Gonzalez then singled to right, scoring both Gerut and Edgar Gonzalez, after which Chase Headley singled to again load the bases.
After Joel Zumaya relieved Fossum, Hairston delivered a single to drive in Giles and Adrian Gonzalez.
The four-run inning made a winner out of Heath Bell (5-3), even though he gave up the tying run in the only inning he worked.