Oswalt will have an MRI on Monday but said he doubts he will make his next start. The back issues are nothing new for Oswalt, who had a stint on the 15-day disabled list earlier this season with lower back inflammation.
"I felt it for the last couple days," Oswalt said. "I tried to pitch through it, it didn't really get any better."
Oswalt gave up four runs on five hits in two innings while striking out one. He allowed a home run to Jon Jay in the first, and was touched for three runs in the second before being lifted for pinch-hitter Cliff Lee in the Phillies' half of the third inning. He was favoring his back during the second inning, and drew brief visits from catcher Carlos Ruiz and shortstop Jimmy Rollins.
Looking forward, both Oswalt and Phillies manager Charlie Manuel were unsure if Oswalt would go on the disabled list for a second time this year.
"We'll have to wait and see," Manuel said. "When we get back, whatever the doctor says, we'll do something that's the best for him and our team."
When asked if he thought the latest setback was a threat to end his career, Oswalt was reserved in his response, yet remained somewhat optimistic.
"You throw as long as you can throw, and if you can't throw no more, you can't throw no more," Oswalt said. "I'm going to keep throwing as long as I can, and hopefully it's not gotten to the point where I can't throw no more."
Kyle Kendrick, who had not pitched since his June 15 start against Florida, relieved Oswalt to start the third. Kendrick went four innings, allowing two runs on five hits.
Oswalt was coming off a loss in his last start against Seattle on June 17, and entered the game with a 4-5 record and 3.38 ERA. Since his return from the DL on May 17, Oswalt is 1-5 with a 4.06 ERA. The velocity on his fastball has dropped this season, and the right-hander has had to adjust accordingly.
"He relies more on command and hitting spots now, but that might be because he's got trouble with his back," Manuel said.
Oswalt's last MRI wasn't exactly welcome news to the three-time All-Star, revealing two degenerated disks in his back. But whatever the prognosis is on Monday, Oswalt says he won't put his future above the team.
"I'm going to do what's best for the team, if I can't pitch, I can't pitch," Oswalt said. "I'm not going to keep going out there and keep being a liability for the bullpen to have to pick me up. If it's gotten to that point, it's gotten to that point."
Austin Laymance is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.