Trevor Cahill needed just 11 pitches to get out of the first inning and retired the first five hitters he faced.

It fell apart for the Oakland right-hander almost as quickly.

Colby Rasmus homered and scored three times and the Toronto Blue Jays scored in three straight innings to chase Cahill on the way to a 7-0 win over the Athletics on Thursday night.

"I thought it would be a good day and just felt too good, almost trying to maybe throw too hard," said Cahill following his third consecutive loss. "It's frustrating because I feel like I've figured it out over a couple of starts and then I'll go into a funk for a couple of starts. There's just been no consistency."

Cahill (9-12) allowed seven runs and nine hits over 5 1-3 innings and lost for the seventh time in his last 10 starts. Since beginning the season 6-0, Cahill is 3-12 with a 5.30 ERA.

That's not what the A's expected from their 18-game winner in 2010. Cahill has won just once since June 25 and is fourth in the American League in walks (68).

"There are certain innings that he has great stuff, and other innings the ball comes up in the zone," Oakland manager Bob Melvin said. "He's just having trouble finding a consistent release point. I thought in the first inning that was as good a stuff as I've seen him have."

Colby Rasmus homered and scored three times for Toronto, though it hardly mattered.

The A's managed just three hits off Blue Jays starter Ricky Romero, got only two runners to third base and were shut out for the 12th time this season.

Romero struck out six and walked two while recording his second shutout this season and third of his career. He had to pitch out of a series of jams early then retired the final 13 batters he faced.

Edwin Encarnacion and Brett Lawrie had RBI singles while Jose Bautista doubled and scored in the fourth when Toronto scored three times off Cahill to break the game open.

"I think I was aiming to the outside corner today and it wasn't coming back like it normally does," Cahill said. "If I could put my finger on it I could maybe fix it."

Rasmus, acquired from St. Louis as part of an eight-player trade on July 27, doubled and scored in the second then hit a towering two-run drive off Cahill in the fourth. The home run, Rasmus' third with Toronto and 14th overall, caromed off a sign hanging from the second deck in right field and gave Toronto a 4-0 lead.

He also singled leading off the sixth for his first three-hit game since the trade.

Before getting to Cahill, Rasmus had been mired in a 16-for-71 funk (.225) with his new club.

Encarnacion, meanwhile, remained one of the hottest hitters in the American League. The Blue Jays designated hitter singled in Bautista in the fourth and scored on Rasmus' home run. He has reached safely in 17 consecutive games.

Romero (12-9) did the rest, although the left-hander labored at times.

He pitched out of a two-on, no-out jam in the second then wriggled out of trouble again after Oakland loaded the bases in the third by getting hot-hitting Brandon Allen to foul out to first. Allen, called up from the minors on Saturday, was in a 9-for-16 stretch before popping out.

Romero, who shut out the St. Louis Cardinals on four hits June 6, settled down after that and allowed only one hit the rest of the way. He improved to 4-0 in five career starts against the A's.

Adam Lind added an RBI single off Cahill in the fifth and J.P. Arenciba drove in two runs in the sixth to chase the Oakland right-hander, who is in the worst slum of his career.

The A's fell to 2-5 on their homestand.

NOTES: Melvin made his pitchers take fielding practice before the game. Oakland went into the night tied with Texas for most errors in the AL. ... The A's placed RHP Trystan Magnuson on the 15-day disabled list with tendinitis in his pitching shoulder and called up LHP Jordan Norberto from Triple-A Sacramento. ... LHP Luis Perez, who earned the win in relief of Mills on Sunday,is scheduled take Mills' spot in the rotation and start Saturday at Oakland. .. The Blue Jays plan to call up right-hander Joel Carreno from Double-A New Hampshire. ... LHP Brett Cecil (4-5) goes for his first win since July 29 when he pitches for the Blue Jays on Friday. Cecil took the loss against Oakland on Aug. 9 when he allowed three runs in seven innings. ... RHP Rich Harden (3-2), who beat the Blue Jays on Aug. 9, pitches for the A's.