Armando Galarraga threw 6 1/3 solid innings, but Kurt Suzuki's walk-off single in the ninth handed Detroit a 3-2 loss, allowing the White Sox to gain a game in the American League Central standings.
"This is the last time I'll say it," Leyland said. "I've said it a lot this year, but this is the last time. I thought that was a lineup that'd score some runs.
"That's been the story this year. ... We didn't hit. That sums it up."
The A's didn't hit much, either, but they did when they needed to.
Adam Kennedy opened the ninth with a single off Zach Miner, then took second on a sacrifice bunt by Rajai Davis. Suzuki sent a line drive to left, and Kennedy beat Ryan Raburn's throw for the win.
Galarraga, meanwhile, did everything the Tigers needed him to do to win the ballgame.
Before Saturday's game, Leyland said his second-year starter was pitching too slowly. He didn't want to throw Galarraga's rhythm off, but he wanted him to pick up the pace.
Galarraga's pace slowed to a crawl in the second inning. He threw 27 pitches, loading the bases -- twice -- as the A's sent eight to the plate.
He limited the damage, though, as he held Oakland to two runs in the inning. Galarraga cruised from that point, retiring 13 of the final 16 batters he faced.
"It's getting better," Galarraga said of his pace. "I was making my pitches. I was throwing my changeup to the corners and my fastball was good. I felt good."
Leyland added, "He got off to a little bit of a slow start, but he did a great job."
Detroit got out to a 1-0 lead in the first. Curtis Granderson started the game with a double. He took third on a single by Placido Polanco, then scored when Carlos Guillen grounded into a forceout.
The Tigers had something going in the fourth, but couldn't capitalize. Miguel Cabrera walked and advanced to third on a single by Aubrey Huff, putting runners on the corners with one away. Clete Thomas went down swinging, then Brandon Inge grounded to short to end the inning.
They were able to tie things up in the sixth. Polanco led off with a single and advanced to second on a groundout by Guillen. Cabrera singled off the right-field wall to score Polanco, extending his hitting streak to seven games.
The A's tried piecing their game-winning rally together an inning earlier. Ryan Perry slowed them down, though.
Scott Hairston and Ryan Sweeney delivered back-to-back singles to start eighth inning. After Mark Ellis struck out on a bunt attempt, Perry walked Jack Cust to load the bases.
Perry retired Daric Barton with a popout to third, then got Cliff Pennington to ground to first to end the inning. He went 1 2/3 innings and struck out two.
"He's done well," Leyland said. "He's gained some valuable experience. ... He threw exceptionally well tonight."