Arrieta pitched three-hit ball into the fifth inning, leading Baltimore to a 3-1 win over the Toronto Blue Jays on Saturday.
In his last two outings, Arrieta has given up five hits in 8 2-3 scoreless innings. Arrieta struck out two and walked three in 4 2-3 innings on Saturday.
"Today was the best sequence I've had from start to finish in a long time," Arrieta said. "Not just this spring, but since I can remember."
Arrieta is contending with Zach Britton, who threw 3 2-3 innings of one-hit ball against Boston on Friday, Steve Johnson, who'll pitch on Sunday against Minnesota and Brian Matusz, who may also be used out of the bullpen.
"No matter the situation, I try to come in and prove myself every year. As far as the evaluation process I want to show progress anytime I go out there in a lot of areas," Arrieta said.
Manager Buck Showalter, whose called the fifth start quandary "a good difficult" decision, wasn't as impressed with Arrieta's outing.
"I don't mean to be picky, but that's the type of outing, carrying that kind of stuff that he should go deep," Showalter said.
"I think he had seven three-ball counts. He only had eight of 20 first-ball strikes, so there's room for improvement. That'll tell you how good his stuff was today because he got by with it."
Happ, who's still not a contender for the Blue Jays' fifth starter role despite Ricky Romero's struggles, allowed two runs on four hits in 3 2-3 innings while striking out six and walking none. All the Orioles hits against Happ were doubles — two by non-roster outfielder Lew Ford, who's batting .500 this spring.
He'll be either a reliever in Toronto's bullpen or a starter at Triple-A. It's not what he's looking for.
Happ will soon discuss his situation with Blue Jays' general manager Alex Anthopoulos.
"I'm trying to keep the positivity going and not cause a big deal here," Happ said. "That stuff will be handled in private, I hope."
When asked if he would initiate a discussion with the GM before his next scheduled start, Happ said he probably would.
"We're kind of getting down to it a little bit, so I don't know," he said.
Mark DeRosa drove in Toronto's run with a sixth-inning sacrifice fly.
Catcher J.P. Arencibia returned to the team on Saturday after his stint with Team USA in the World Baseball Classic. He particularly enjoyed facing Blue Jays teammates Edwin Encarnacion and Jose Reyes, who are playing for the Dominican Republic.
"I couldn't hear anything anyways. Against the D.R., the game was pretty slam-packed. It was loud the entire game," Arencibia said.
NOTES: The Orioles optioned RHP Dylan Bundy to Double-A Bowie. Bundy, the team's No. 1 draft pick in 2011, was 1-1 with a 1.13 ERA in four spring games, but walked six batters in eight innings. Baltimore also optioned RHP Todd Redmond to Triple A-Norfolk. ... Baltimore CF Adam Jones will return to the team from the World Baseball Classic on Sunday, but won't play until Wednesday, Showalter said. ... Blue Jays RHP R.A. Dickey also returned from the WBC. His next start has yet to be decided. ... Toronto reassigned five players to minor league camp: LHPs Alex Hinshaw, Tommy Hottovy, Juan Perez, RHP Neil Wagner and C Jack Murphy.