CINCINNATI (AP) — Who can explain this?

Roy Oswalt got his 19th career victory against the Cincinnati Reds on Monday night, leading the Houston Astros to a 5-4 victory that left everybody amazed by one of baseball’s most mind-boggling marks.

How could any pitcher go 19-1 against a team?

“I have no idea,” said Oswalt (5-2), who gave up a pair of solo homers in seven innings. “The good thing is every time I pitch against them, I get run support. I hope it doesn’t change.”

Luke Scott provided the big hit this time, a tiebreaking three-run homer in the eighth off reliever Todd Coffey that left the Astros 5-1 against the Reds this season.

Oswalt’s success against the Reds is unprecedented. The right-hander won his first 15 decisions against them, and improved to 19-1 career on Monday.

Explain that?

“Have you see Roy pitch?” Houston’s Lance Berkman said. “I wouldn’t be surprised if he’s 19-1 against anybody. He’s the best in the game, as far as I’m concerned.”

He’ll get no argument from the Reds, who thought they had Oswalt in trouble after Adam Dunn and Alex Gonzalez hit back-to-back homers in the second inning — only the second time in Oswalt’s 22 career starts against the Reds that he gave up two homers.

“He’s just so good,” Dunn said. “We jumped on him early, but to his credit, like he always does, if you don’t get five right there, you’re not going to get it.”

After giving up the two homers, Oswalt was determined to stop the Reds from getting any more runs.

“Coming out of the bullpen, I felt better than I did in a long time,” Oswalt said. “The ball was jumping out of my hand. My curve was great. I thought I might go seven or eight innings without giving up a hit.”

Dan Wheeler gave up Gonzalez’s two-run homer in the ninth before getting his sixth save in seven chances.

Kyle Lohse (1-3) matched Oswalt until the eighth, when Craig Biggio led off with a single. After Mike Stanton walked Berkman, Coffey sprinted from the bullpen to the mound and gave up Scott’s homer to right field on a full-count changeup that was right down the middle.

It was the latest meltdown by a bullpen that has just one save since April 15.

“I was going after him,” Coffey said. “I was thinking, I’ve got him right here. Let’s get him out.”