Oswalt was still competitive through five innings in a 3-3 game. Then the Angels broke it open with nine runs in the sixth inning off Oswalt and reliever Robbie Ross. Kendrys Morales hit two home runs and drove in six runs in the sixth, becoming the third player in history to connect from each side of the plate in the same inning.
Oswalt, who was skipped in his last start because of tightness in his lower back and was on the mound for the first time since July 17, ended up allowing eight runs on 11 hits, including three home runs, in 5 1/3 innings. He is now 3-2 with a 6.49 ERA in six starts overall with the Rangers.
"I felt pretty good, but it was the first time out there in 11 or 12 days and I just didn't fall into sync," Oswalt said. "I never got any downward plane. I kept getting everything up, up, up. It was just a lack of not throwing."
Oswalt's rough night came less than 24 hours before the non-waiver Trade Deadline as the Rangers were conducting multiple conversations with other clubs about acquiring pitching. The Rangers were investigating the possibility of adding a starter or a reliever. Rumors swirled around the Rangers all day regarding Red Sox right-hander Josh Beckett and Phillies left-hander Cliff Lee, but their hefty contracts seemed to keep anything from gaining traction on Monday night.
The Rangers, who still have Tuesday to make a move after reassessing Oswalt's latest start, now lead the Angels and the Athletics by four games in the American League West.
"We can't get too disappointed," shortstop Elvis Andrus said. "We've still got three games to go against them. We've still got a chance to win the series. We'll turn the page and be ready tomorrow."
"Any series, you want to take that first game," Angels outfielder Torii Hunter said. "You enjoy tonight, you wake up tomorrow, and you have to have amnesia -- forget about today. But we'd like to ride on this, remember what we did today and build off it."
The nine-run inning tied the biggest by an American League team this season. The White Sox did it in the fifth inning in a 19-2 win over the Rangers on July 3. Oswalt was on the mound and took the brunt of that one, too.
"Up until the fifth inning, it was a very competitive game," Rangers manager Ron Washington said. "Oswalt threw some good pitches, some good fastballs and some breaking balls. It was a very competitive game, we just couldn't stop the bleeding until then."
The Rangers did get a hit with a runner in scoring position. The Angels were leading 1-0 on Maicer Izturis' home run when the Rangers opened the bottom of the second inning with a walk to Nelson Cruz and a double by Josh Hamilton. Michael Young's sacrifice fly scored one run and David Murphy's double brought home another run.
Murphy's double ended the Rangers' streak of going hitless in 29 at-bats with runners in scoring position. It was the longest such streak for the Rangers since an 0-for-35 in 1988.
The Rangers also hit three home runs -- by Hamilton, Cruz and Mike Napoli -- and scored more than five runs for only the fourth time in 22 games this month.
"It was nice to see the offense going, we just couldn't stop them," Washington said.
Ervin Santana picked up the victory for the Angels after going 0-3 with a 9.41 ERA in his previous five starts. That included giving up six runs in 1 2/3 innings in a 9-2 loss to the Rangers in his previous start.
"The way we set a tone is hopefully with our starting pitching," Angels manager Mike Scioscia said. "We need to get back into that. We've been searching for those five guys to go out there and give us a chance to win every night. So, in some sense, the tone was Ervin getting through five and keeping us in the game. But there's a lot of baseball left, and really, we need to go out there tomorrow and just start some momentum again."