Boston scored four in the eighth to take the lead against Rodriguez, only to see Gagne give it back in the ninth on Friday night when the Los Angeles Angels rallied to beat the Red Sox 7-5 and split a day-night doubleheader.
"Same things that will make you laugh will make you cry," Red Sox manager Terry Francona said. "They turn right around and do it to us."
Clay Buchholz gave Boston six strong innings in his major league debut to pace an 8-4 win in the afternoon. John Lackey failed to win his 16th game in the afternoon, and Josh Beckett did the same in the nightcap.
Ervin Santana pitched well in his return from the minors, retiring the first 13 batters he faced in the night game. But his bid for his first victory since June was spoiled when David Ortiz and Manny Ramirez hit back-to-back RBI doubles off Rodriguez (5-2) to give Boston a 5-4 lead.
The Angels had little trouble with Gagne (3-1), who was not available for comment after the game. Boston's key acquisition at the trading deadline, the former Rangers closer allowed three runs and three hits and a walk in one inning, giving up a game-tying single to Orlando Cabrera and a tiebreaking, two-run double to Vladimir Guerrero.
"That's as much of a rollercoaster as you can be on," Angels manager Mike Scioscia said. "That's one of the best comebacks we've had."
After blowing the save in the eighth, Rodriguez settled down in the ninth and retired the Red Sox in order. He was charged with one run on two hits in 1 2/3 innings.
K-Rod struck out Kevin Youkilis in the ninth, though replays showed the third strike was a foul ball; Youkilis and Francona were ejected arguing the call.
"My second inning, my location was much better, and you saw the results," Rodriguez said.
- To make room for Santana, the Angels optioned INF Matt Brown to the minors.
- C Ryan Budde recorded his first major league hit, a line drive off Lugo's glove in the fifth.
- Ramirez was hit by a pitch twice in the first game, the second time in his career he has been hit twice in a game.
- Jordan Leandre, 7, a patient at the Dana Farber Cancer Institute, sang the national anthem before the nightcap and got a huge ovation when he ran the bases.
- SS Julio Lugo committed two errors in the night game.