"He did well in Triple-A," Baltimore manager Dave Trembley said. "The reports are that it's time for him to see if he can do it at this level."
Olson, who was 1-1 with a 1.85 ERA in five starts with Norfolk, arrived amid a flurry of roster moves. The Orioles also recalled right-handed reliever Bob McCrory from the Tides, optioned infielder Brandon Fahey to Norfolk and designated ineffective right-hander Greg Aquino for assignment.
"We decided to go back to 13 pitchers," Trembley said. "Obviously, the decision was really made by the recent events of the road trip -- the split doubleheader, the travel, the rainouts and all those kind of things."
Olson struggled with the Orioles in 2007, going 1-3 with a 7.79 ERA in seven starts. He last pitched Saturday, and was limited to two innings in anticipation that he might be needed to face the Rays.
"Hopefully what he did down there is what he didn't do here," Trembley said. "He commanded his fastball down there. That's what he needs to do at the big league level."
Trembley said he hopes Olson has learned to trust his breaking ball and set it up with his fastball, and that he won't try to be something he's not on the mound.
"It all starts with him with strike one," Trembley said. "He's got to command the fastball. Major League hitters, with all due respect, are a little more sophisticated. They know their strike zone, they don't swing at bad pitches and they'll work the count. So we need him to show that he can throw strikes."
McCrory bolsters a bullpen that has been called on to work 22 1/3 innings in the past seven games. A fourth-round pick in the 2003 Draft, McCrory went 0-2 with a 1.80 ERA and four saves in nine games with Norfolk.
He learned he was being recalled when Norfolk pitching coach Larry McCall stopped him after Monday's game in Charlotte and delivered the good news.
"Honestly, I couldn't quit shaking there for a bit," said McCrory, 25, who underwent Tommy John ligament replacement surgery on his right arm in 2005, and was later converted from a starter to a closer. "It's something you dream of your whole life, and it finally came true."
The promotion came as a surprise to McCrory, even though Trembley acknowledged that he, pitching coach Rick Krantiz and bullpen coach Alan Dunn had agreed that McCrory would be in the Major Leagues by mid-May.
"There were a lot of guys in Triple-A throwing really well and had big league experience," McCrory said. "I'm excited, don't get me wrong, but it shocked me when I heard."
Fahey, who competed with Luis Hernandez to be the Orioles' starting shortstop in Spring Training, but took over a utility role when he lost that battle, was optioned, as he had Minor League options remaining. The move gives Trembley a longer look at infielder Eider Torres, who was recalled over the weekend for his first taste of the Major Leagues.
"Torres just got here," Trembley said. "I think Torres deserves a little bit longer look than he's got. Torres put some numbers up down there offensively. I'd like to see if he can help us in that area."
Fahey, who hit .200 (5-for-25) with one RBI in 15 games, will be used at multiple positions at Norfolk, Trembley said. "He won't play just one slot. He comes back here and that's what he is, he'll be that [utility] guy," the manager added.
Aquino, who won a spot on the Opening Day roster after going 1-0 with a 2.19 ERA in 10 games in Spring Training, was nowhere near as effective once the regular season began. He allowed 11 hits and walked seven in 6 1/3 innings over six games, working to a 14.21 ERA.
"The times that he did pitch, he didn't show good enough command," Trembley said of Aquino. "Secondly, I didn't pitch him enough, which may have factored into it. Three, he's designated for assignment. He clears waivers and wants to accept the assignment to go to Norfolk, he should go there and get an opportunity to pitch."
Pete Kerzel is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.