TORONTO (AP) -- With his first major league start in the books, Kevin Gausman was looking forward to a good night's rest.
Edwin Encarnacion hit his fifth career grand slam, J.P. Arencibia homered and drove in four runs and the Toronto Blue Jays beat Baltimore 12-6 on Thursday night, spoiling Gausman's Orioles debut.
"Definitely a learning experience for me but it was awesome," Gausman said. "It was everything I could have imagined and more.
"I've been waiting my entire life for this," he added. "I haven't been able to sleep very much lately. That was something that was kind of great to get out of the way. Hopefully I can sleep tonight."
The fourth overall pick in the 2012 draft, Gausman allowed four runs and seven hits in five innings. The right-hander walked two and struck out five.
"He gave us a chance to win against a team swinging the bat as hot as anybody," Orioles manager Buck Showalter said. "I thought he handled himself the way you'd like to see a young pitcher handle himself. He's only going to get better."
The youngest starter in the AL at 22 years and 137 days, Gausman showed some veteran composure in the third, loading the bases with none out before retiring the next three batters.
"His changeup was a big pitch for him tonight and he was able to use it in some key situations," catcher Matt Wieters said. "The slider was there if we needed it, too.
"That's a good hitting team and a good hitting fastball team and he was able to make some balls miss some barrels," Wieters added.
Even Blue Jays manager John Gibbons was impressed.
"He's got a great arm," Gibbons said. "He pitched with good composure. He looks like he belongs out there. For a debut he did a heck of a job."
Promoted from Double-A Bowie to face Toronto, Gausman learned that big league hitters are a cut above the opponents he's been facing.
"I threw a great changeup 3-2 to (Colby) Rasmus and he just kind of spit on it," Gausman said. "At this level, those guys are so good it's kind of crazy."
Gausman (0-1) is the 11th pitcher to start for Baltimore this year. The Orioles used 12 starters all of last season.
Baltimore's Chris Davis hit his major league leading 15th home run, a leadoff shot in the fourth. Nick Markakis and Adam Jones hit back-to-back homers off Brandon Morrow to start the eighth but it wasn't enough for the Orioles, who lost for the seventh time in nine games.
Baltimore's Manny Machado went 3 for 4 with three doubles, boosting his major league-leading total to 21.
Morrow (2-3) allowed six runs and a season-high 10 hits in seven-plus innings. He walked one and struck out five.
"It's frustrating for me to go out give up the two home runs without getting an out there in the eighth," Morrow said. "It's a good win, but it put a sour taste in my mouth."
Brett Cecil and Brad Lincoln each worked one inning of scoreless relief as Toronto won for the third time in four games.
Machado gave the Orioles an early lead with a two-run double in the third. Davis made it 3-0 by homering on Morrow's first pitch of the fourth, but the Blue Jays rallied with two runs off Gausman in the bottom half. Adam Lind and Arencibia led off with consecutive doubles and Emilio Bonifacio hit a sacrifice fly.
Arencibia put the Blue Jays in front with a two-out, first-pitch drive in the fifth for his 11th homer.
Troy Patton was replaced after issuing back-to-back two-out walks in the sixth. Pedro Strop came on and walked Jose Bautista before Encarnacion homered off the left field foul screen, Toronto's first grand slam this season.
Five of the eight walks issued by Baltimore pitchers came around to score.
"You like your chances when you score six but not when you walk that many people," Showalter said.
After Alexi Casilla hit a sacrifice fly in the seventh, Markakis hit his fifth home run in the eighth and Jones followed with his seventh. It's the third time this season the Orioles have hit consecutive homers.
Toronto put it away with four runs off T.J. McFarland in a bat-around eighth. Anthony Gose scored from second on a passed ball after Wieters threw to second, Arencibia hit an RBI grounder, Brett Lawrie singled home a run and Rasmus hit a sacrifice fly.