Arencibia hit a three-run double in the seventh inning and the Blue Jays rallied from a five-run deficit to beat the Detroit Tigers 8-6 on Wednesday.
Toronto had opened a season of high expectations with five losses in seven games.
"No reason to panic, but when you see it slipping away in the fifth or sixth inning, it was nice for the bats to come alive," said DeRosa, whose pinch-hit double in the sixth got the comeback started in earnest. "We obviously didn't get off to the start we wanted to, but we fought."
Detroit led 6-1 in the sixth, but starter Rick Porcello allowed hits to the first three batters that inning. They all eventually scored, and Toronto added four more runs the following inning.
Brayan Villarreal (0-1) came on with one on and one out in the seventh and proceeded to walk three straight hitters, forcing in a run. Arencibia followed with a drive to the gap in left-centre off Octavio Dotel to make it 8-6.
"It was nice to finally get a few hits and walks and guys grinding out at-bats, and string it all in the same inning," Arencibia said. "To score, you need to be able to do that collectively in an inning."
Aaron Loup (1-0) pitched a scoreless sixth for the Blue Jays. Casey Janssen, the last of five Toronto relievers, pitched a perfect ninth for his second save.
The game started after a rain delay of 2 hours, 29 minutes, and it was also raining when the Tigers made the final out.
The Blue Jays fell behind early. Mark Buehrle, acquired in the same off-season trade that brought Jose Reyes and Josh Johnson to Toronto, allowed six runs — five earned — in 4 1-3 innings.
Three of those runs came home after Buehrle left the game in the fifth. Reliever Steve Delabar allowed bases-loaded walks to Victor Martinez and pinch-hitter Andy Dirks, and Jhonny Peralta added an RBI single to make it 6-1.
But Porcello didn't get another out. He allowed four runs and eight hits in five-plus innings and left the lead to what is already a beleaguered Detroit bullpen. The Tigers don't have a set closer. Manager Jim Leyland says he's willing to use anyone to pitch with a lead in the ninth inning — but he never even got to make that decision Wednesday.
Edwin Encarnacion doubled in a run to chase Porcello, and DeRosa followed with a two-run double off Darin Downs. That set the stage for the seventh inning, when the Blue Jays took the lead.
"We really didn't give ourselves a chance," Leyland said. "We walked the guys. You don't give yourself a chance when you walk guys."
Toronto, meanwhile, blanked the Tigers over the last four innings. After Loup's scoreless frame, Brett Cecil pitched the seventh and Darren Oliver worked the eighth.
Oliver got a bizarre assist when Austin Jackson's line drive hit him around the left elbow and bounced right to DeRosa at first base for an easy 1-3 putout. The left-hander was able to continue.
"You never like to see a teammate get hit with a line drive," DeRosa said. "But for the ball to carom right to me — maybe things are starting to change a little bit."
Dotel had his own injury scare in the top of the inning when a one-hopper by Emilio Bonifacio hit him in the groin area. Dotel was also able to continue pitching.
NOTES: Encarnacion snapped an 0-for-19 skid by doubling in the fourth and sixth. ... Tigers 1B Prince Fielder helped his team with his legs, beating out a potential double-play grounder in the first to drive home a run and later reaching on an infield single. ... Jose Valverde, who was Detroit's closer last year before being demoted during the post-season, threw a bullpen session in Lakeland, Fla., on Wednesday. He's expected to pitch Friday in an extended spring training game, and again Monday in a scrimmage. Valverde, a free agent, signed a minor league deal with Detroit last week. ... All nine runners inherited by relievers came in to score. ... Detroit RHP Doug Fister (1-0) takes the mound against Toronto RHP Josh Johnson (0-0) on Thursday, weather permitting.