Cecil struck out a season-best eight against the Athletics but Oakland extended its winning streak to six games with a 7-2 victory over Toronto.
A seventh-inning meltdown by relievers Chad Beck and J.A. Happ resulted in five two-out runs for the A's. The loss snapped a three-game win streak by the Blue Jays (48-48) and wasted home runs by J.P. Arencibia and Travis Snider.
"Brett, I thought, was outstanding with six innings of work but where we were in the lineup I felt that going to a right-hander in the seventh (was the right move)," said Blue Jays manager John Farrell. "Unfortunately, we contributed to that big inning in the seventh with some walks.
"It was too much to overcome at that point."
Travis Blackley also struck out a season-best eight and Yoenis Cespedes drove in three runs for Oakland. Derek Norris had a two-run homer for Oakland.
Oakland's previous five wins — including a four-game sweep of the New York Yankees — had been by one run and they improved their record in July to 15-2.
"We're on a roll," Blackley said. "We're enjoying the game and we expect to be able to come up big in certain situations and we've doing it over and over again."
Blackley (3-2) held the Blue Jays to five hits, one walk, and a solo home run by Snider over seven innings.
Cecil (2-3) held the A's to five hits, two walks and two runs, both on a two-out home run by Norris in the second. The game got away from the Blue Jays in the seventh even though Beck retired the first two batters of the inning.
"In two innings the third out was obviously a little elusive," Farrell said. "Two runs in the second and five in the seventh but the way Blackley was pitching tonight that was obviously too big of hole for us to come back from."
Cecil stayed philosophical despite the loss.
"Things happen," he said. "I told John I felt like I had another one in me. But with the righties coming up and one the guys who did damage to me, it's understandable.
"I had 94 pitches. I didn't see anything wrong with taking me out of the game."
Blackley was frustrated by his performance, even though he earned his third consecutive victory.
"I felt a bit like a fish out of water early, just didn't have a rhythm," said Blackley. "The cutter was disgustingly bad today, it didn't work at all.
"Luckily the curveball was just phenomenal today. I was able to throw it for strikes and below the zone for swings. That pretty much changed the game for me today because I really didn't hit many spots with any other pitch."
Cecil nearly matched Blackley.
"Brett used his change-up, his curveball and his cutter in to right-handers and had a number of batters off-balance," Farrell said.
Arencibia's 16th homer of the season and his third in three games for the Blue Jays came in the ninth against Jim Miller. Toronto's catcher went 2-for-4 on the game. Brett Lawrie of Langley, B.C., chipped in with three hits for the Jays.
Oakland (52-44) took a 2-0 lead in the second. Cecil retired his first five batters before allowing a single to Brandon Inge and on the next pitch Norris hit his third homer of the season.
It was the eighth home run allowed by Cecil in seven starts since his recall from the minors.
"As long as he doesn't walk people in front of the home runs, you can live with the solo home runs," Farrell said. "But Inge stayed inside a pitch to get a base hit the other way to get the first guy on with two outs.
"But two runs over six innings? Brett did his job."
Snider got one back for the Blue Jays with his second homer of the season to lead off the third. Snider was recalled from triple-A Las Vegas on Friday and also homered in Sunday's 15-7 victory at Boston.
Blackley had not allowed a home run in his previous eight games.
Pitchers controlled the game until the seventh when Brandon Hicks doubled against Beck with two out and Jemile Weeks followed with a triple.
"We capitalized on the big moments that we needed to," Weeks said. "Just winning in itself is contagious and once you get the belief that you can win, it's easier to come about finding that W."
Happ allowed a double to Coco Crisp. He walked the next two batters to load the bases for Cespedes who singled to the left-field gap to clear the bases and extend Oakland's lead to 7-1.
"We were in this game, we were battling and I took us right out of it so it's not a good feeling," Happ said "Crisp was a .200 hitter against left-handers and I thought that was the move to turn him around to the right side and he hits the first pitch inside the bag for a double," Farrell said.
Notes: Attendance at Rogers Centre was 25,686..... Reliever Sergio Santos had shoulder surgery on Tuesday. He has been on the disabled list since April 21 with what was listed as shoulder inflammation. The club is not expected to reveal the results of the surgery until Wednesday. ...Reliever Jason Frasor, who was put on the disabled list on Saturday with tightness in his right forearm, had an MRI that revealed only inflammation. He will not throw for two weeks. ...Brandon Morrow is scheduled to throw batting practice on Wednesday in Dunedin, Fla., and if it goes well is expected to begin his rehabilitation assignment on Sunday. He suffered a strained left oblique muscle in his start on June 11. ...Left-hander Ricky Romero (8-6, 5.22 earned-run average), who is 0-5 with an 8.33 ERA in his past five starts, will start for Toronto on Wednesday against Oakland's A.J. Griffin (2-0, 2.70 ERA).