Trailing 2-1 with two outs in the seventh, Hairston's first throwing error of the inning allowed Cameron Maybin to reach first base. Everth Cabrera then singled off Dodgers starter Chris Capuano (9-5) and Jeff Baker drew a walk to load the bases.
Pinch-hitter Yasmani Grandal followed by smacking a tough grounder that Hairston stopped, only to again throw wildly to first, allowing two runs to score.
The next batter, pinch-hitter Alexi Amarista, delivered an RBI single and the Padres went on to add three runs over the final two innings to win going away.
Jason Marquis (2-5) earned the victory, yielding two runs on six hits over six full innings as San Diego took two out of three from the Dodgers.
Hairston and Andre Ethier each provided an RBI for second-place Los Angeles, which fell 1 1/2 games behind San Francisco in the National League West.