Tigers starter Anibal Sanchez gave up three homers in five innings of work, with Astros catcher Jason Castro walloping a two-run shot to right-center field in the fifth inning that made it 9-4. Castro's six homers this spring are a team-high and match his regular-season total of last year.
Sanchez allowed 11 hits and nine runs in five innings, throwing 101 pitches.
Singleton, who will begin the season at Triple-A, homered to right field in the first inning and belted a second homer in the Astros' five-run third inning. Rick Ankiel also had a two-run double in the third and added a homer in the sixth.
Astros starter Philip Humber was rolling through the fourth before the Tigers took advantage of some poor defense and scored four times, including a three-run homer by Prince Fielder, to cut the Houston lead to 7-4. Humber pitched a 1-2-3 sixth.
"I don't think I could have asked for a better Spring Training as far as how I threw the ball and the results I got," said Humber, who will start Wednesday against the Rangers. "I couldn't be in a better position going into the season, but it's one day at a time. I feel healthy and feel I have all my pitches where I want them."
Up next: The Astros return to Houston to face the Chicago Cubs in an exhibition game at Minute Maid Park at 7:05 p.m. CT. Right-hander Alex White, who learned Thursday he would begin the season in the bullpen in long relief, will get the start for the Astros.