By the time his head stopped spinning in the fifth at Angel Stadium, however, Arrieta was in the Orioles dugout smarting from his shortest stint since July.
"They weren't trying to do too much," Arrieta said of the Angels. "They were just trying to play small ball and keep the inning going. Those three walks there really hurt me there. I just couldn't make the pitch to get out of the inning, that's what it comes down to."
Arrieta (1-1), who had allowed just six earned runs in his first three starts this season, was charged with five earned runs, eight hits and three walks in just 4 1/3 innings.
Heading into the fifth, Arrieta and Angels right-hander Jered Weaver, last year's American League Cy Young Award runner-up, were dominant.
"I was pretty sure we were going to have a pretty good pitcher's duel there after the first four innings," Orioles catcher Matt Wieters said.
Weaver took a perfect-game bid into the fifth, when Adam Jones reached on an infield single and Wieters crushed a 3-0 fastball into the right-field stands for the catcher's fifth homer of the season.
"I got the green light and it is something where you know Weaver's tough, so if you can get in a fastball count where you know you are going to get a fastball you can put a pretty good swing on it," Wieters said.
The Orioles' 2-0 lead was short-lived.
"We've had some trouble this year with shutdown innings after we score," manager Buck Showalter said. "We've got to go out there and, especially where we are in the order, shut that inning down. That's the game. We get a shutdown there, we are on our way."
Arrieta hadn't allowed a hit since a leadoff single by Erick Aybar in the first. He retired 12 straight before Torii Hunter singled to start the bottom of the fifth. Hunter moved to second on an errant pickoff throw by Arrieta -- his second throwing error of the game -- and to third on a wild pitch.
Hunter then scored on Mark Trumbo's RBI single. Arrieta sandwiched in a strikeout between two walks before Aybar singled a run home and Bobby Abreu laced a two-run single. Arrieta walked Albert Pujols to load the bases, and surrendered another RBI single to Kendrys Morales before he was mercifully pulled from the 35-pitch inning.
"I wouldn't say it unsettled me," Arrieta said of the error. "It was just a very, very tough mental mistake there, I made two of them."
Showalter didn't think the error led to Arrieta's unraveling.
"I hate to think that was it," the manager said. "We are always looking for something. I know you guys are looking for something that pushed the button. But I don't know if that's it. I'm more interested in the mentality of a shutdown inning after your team scores two runs off one of the best pitchers in the American League. You got to pitch that next inning like the seventh game of the World Series."
Arrieta's line could have been much worse, but reliever Matt Lindstrom induced two bases-loaded comebackers to limit the damage.
"The first four innings were very good," Arrieta said. "and I was on pace to have a very good outing tonight, the pitch count was down. So it's just frustrating that when we put up two runs in the fifth and I am not able to have a shutdown inning and extend my outing even further it's frustrating. Not really for myself but for the team. We get two runs off a guy like Weaver we need to do what we can to win the game."
Arrieta could only shake his head at going from cruising to losing.