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 Tigers bid farewell to Lakeland, Fla., with a 1:05 p.m. ET game against the Rays at Joker Marchant Stadium, starting off a home-and-home series against Tampa Bay to close out Grapefruit League play. Max Scherzer will make his final start of what has been an outstanding spring for him when he takes the mound opposite Jeremy Hellickson. Brayan Villarreal, Phil Coke and Octavio Dotel are also scheduled to pitch; the game is available live on Gameday Audio.