Romero allowed eight runs in 1 1/3 innings, the shortest start of his career, while catcher J.P. Arencibia broke his right hand from a foul tip in an eight-run second inning. It was the Blue Jays' largest shutout loss in club history.
"Embarrassed," said Romero, when describing how he felt after losing his sixth successive start. "This team plays their asses off every night and for me to come out and have a tough performance ... it's a complete embarrassment."
Romero (8-7) allowed four hits and six walks (one intentional) and his earned-run average jumped to 10.48 over his past six starts.
It was the Athletics' (53-44) seventh win in a row. It was also the fourth successive start by Romero in which the Blue Jays have failed to score.
A.J. Griffin (3-0) held the Blue Jays (48-49) to three hits and no runs in six innings to win his third start in a row.
"I'm speechless, the lead that I got today," Griffin said. "That's amazing."
Manager John Farrell said Arencibia's fracture is non-displaced and won't require surgery.
"It's unfortunate the way he's been swinging the bat," said Farrell. "It's going to be a little bit of a hole for us to fill at the present."
The absence of Arencibia, who has 16 home runs and 50 RBIs, further depletes a lineup that now has 11 players on the disabled list.
Farrell said the Blue Jays will go with Jeff Mathis and Yan Gomes at catcher, who both played on Wednesday after Arencibia left the game. Gomes caught for Mathis, who pitched the ninth to save the bullpen and gave up two runs on three hits.
After the game, reliever Chad Beck was returned on option to triple-A Las Vegas and right-hander Joel Carreno and left-hander Evan Crawford were recalled from the minors with Arencibia going on the disabled list.
The shortest start of Romero's career before Wednesday was 2 1/3 innings against Boston on July 9, 2010. Farrell said althought Romero's stuff was better than during his previous start on July 18, the command wasn't there.
"We've got to work to get him right," Farrell said. "No question about it, we've talked a lot about what his frame of mind is and yet we've got to work on that to get him untracked."
Romero said he must work on "not thinking too much and not worrying about what's happened in the past and my numbers.
"I'll be here tomorrow to get ready for my next start, that's all you can do," said Romero. "Tonight was just pathetic on my side. As tough as it is sometimes you just have to continue to work hard and not let anything bother you."
Oakland opened the scoring in the first when Jonny Gomes walked and scored from first on a two-out double by Yoenis Cespedes.
Coco Crisp hit two solo home runs for the Athletics while Chris Carter had three RBIs, including one of three solo home runs against Drew Carpenter.
Oakland scored eight in the second, started by a walk to Derek Norris. With one out, Jemile Weeks walked. Crisp singled to left and a run scored when Travis Snider overran the ball for an error. Gomes singled in one run and Josh Reddick doubled in another.
Cespedes was walked intentionally to load the bases and Romero walked Carter to force in a run. Chad Beck replaced Romero and gave up a two-run double to Inge. It was during Inge's at-bat that Arencibia took a foul tip off the hand.
"My hand was pretty bruised up and the umpire asked me if I wanted to call anybody out and I said 'no'," Arencibia said. "If I had to throw a ball we probably would have been in big trouble but thankfully I didn't."
Norris singled in a run, and another scored when Brandon Hicks grounded out to make the score 9-0.
Crisp led off the third against Carpenter with his fourth homer of the season.
He homered against Carpenter again with one out in the fifth. It was his first multi-homer game this season and the third of his career.
Carter hit his sixth homer of the season with one out in the sixth.
Notes: Attendance at Rogers Centre was 23,948. ...Toronto shortstop Yunel Escobar was a late scratch from Wednesday's game because of lower back tightness. ... Tuesday's shoulder surgery on reliever Sergio Santos revealed wear and tear in the joint but no specific tears so a general clean out was performed and Farrell said Wednesday it was "the best news that he could have under the circumstances." Santos should be ready for spring training. ...Brandon Morrow (strained left oblique muscle) threw batting practice on Wednesday and is on schedule to make his first rehabilitation start Sunday for single-a Dunedin. ...Left-hander Aaron Laffey (2-1, 2.77 earned-run average) will start Thursday's series finale against Oakland left-hander Tommy Milone (9-6, 3.34 ERA).