Buchholz lost for the first time this season, and the AL East champion Boston Red Sox rested a couple of regulars while falling to Mark Buehrle and the Toronto Blue Jays, 4-2, on Saturday night.
Having missed more than three months with a strained neck, Buchholz feels like his strength is where it was before the injury. He just needs to fine tune a few things.
"I feel good. Movement on all the pitches is there," he said. "It's just the command and location and where to start it, which is sometimes hard to get better. The velocity is there and the body feels good."
Buchholz (11-1) gave up two earned runs on six hits and two walks in six innings. He had pitched 11 scoreless innings in his previous two starts since coming off the disabled list.
A day after the Red Sox clinched the division title, they lost for just the sixth time in 21 games. Manager John Farrell didn't start second baseman Dustin Pedroia and first baseman Mike Napoli, and used starter Ryan Dempster for an inning of relief.
Buchholz was the first Boston pitcher to start a season 11-0 in his initial 14 starts since Roger Clemens went 13-0 in 1986.
"I thought Clay was pretty sharp and pretty crisp for the time he was out on the mound tonight," Farrell said. "He was fighting to get back out for the seventh, but seeing the progression he's on, I think was a comfortable number of pitches for tonight."
Buchholz broke into a slight grin when he was asked about how hard it is to go undefeated for an entire season.
"It probably could have easily have happened sooner than now," he said. "The guys that play behind me all year have found ways to come back in situations where I came out of the game behind in the game."
Boston's lead over Oakland dropped to 1 1/2 games for the AL's best record and home-field throughout the post-season.
Dempster made his first relief appearance since 2007, working a scoreless eighth. Boston third baseman Will Middlebrooks shifted to first for the first time in his career.
Jonny Gomes and David Ross each drove in a run for the Red Sox.
Adam Lind's RBI double highlighted a three-run fourth that carried the Blue Jays.
Buehrle (12-9) held Boston to one run for the third time in five starts that he's faced them this year. He allowed five hits, striking out five without walking a batter. He reached 200 innings for the 13th straight season.
"Wish it was in a better situation," Buehrle said of reaching the mark again.
Manager John Gibbons was impressed by the left-hander's season.
"Steady Eddy," Gibbons said. "Doing what he has been doing his whole career. You get 25 Buehrles and you are probably gonna have a good year."
Casey Janssen pitched the ninth for his 33rd save in 35 chances.
Toronto's Munenori Kawasaki was ejected by first base umpire Eric Cooper in the eighth after slamming his helmet when he was called out on a close play.
The Blue Jays scored all three runs with two outs in the fourth after Brett Lawrie beat out a routine grounder to short for an infield hit. Lind followed with an RBI double, Rajai Davis added a run-scoring single and Moises Sierra scored from third on Buchholz's errant pickoff throw to first.
Gomes' RBI single cut it to 3-1 in the sixth. Ross' run-scoring grounder sliced it to 3-2 in the seventh after Xander Bogaerts reached second on Lawrie's fielding error at third base.
J.P. Arencibia snapped an 0-for-27 stretch with an RBI single off the Green Monster in the Toronto ninth.
NOTES: Pedroia had started 151 of the team's initial 152 games. He pinch-hit in the seventh and struck out. "The hardest thing is he's not going to know what to do," Farrell said, joking before the game. "He may end up back on the field because we want to get him the heck out of the dugout." ... Middlebrooks knew things would be a different in his debut at first. "I've never played first in my life," he said, standing on the field after batting practice. "The hardest thing for me is going to be how to try and hold the runners on, which way to stand with my footwork." ... Red Sox CF Jacoby Ellsbury, sidelined for his 14th straight game with a broken small bone in his right foot, ran and hit in the cage. The club is planning for his return before the end of the regular season. ... Felix Doubront (10-6, 4.15 ERA) goes for Boston against R.A. Dickey (13-12, 4.21 ERA) in the series — and Boston's home— finale Sunday.