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4/26/2013 11:02 P.M. ET

Bullpen a point of strength so far for Orioles

OAKLAND -- Orioles relief pitcher Darren O'Day pointed to a specific series last year in Boston when he thought the Baltimore bullpen came of age.

In a three-game May series at Fenway Park, the Orioles needed 17 relief appearances (including one from first baseman Chris Davis) to throw 23 innings in a sweep of the Red Sox.

Two games went extra innings, one 13 innings and the other 17 innings. The bullpen allowed one run for an ERA of 0.39.

"Everybody was coming in and throwing two innings and we kept throwing up zeroes," O'Day said. "That set us up for the whole year."

The Orioles are getting the same results this season. The bullpen has an ERA of 2.15 and is averaging about 3 1/3 innings a game.

Take away Pedro Strop's 8.22 ERA and it's even more impressive, with the relievers owning an ERA of 1.27.

"The way the bullpen was constructed last year, you had a good mix of veterans, guys who had been closers and setup guys, and young guys," O'Day said. "The veterans were a big influence and taught the younger guys how to handle tight situations."

Arrieta strikes out eight in first Triple-A start

OAKLAND -- Orioles manager Buck Showalter had to be happy about Jake Arrieta's effort Friday night, even if it was 3,000 miles away.

Arrieta, who started the season in the Orioles' rotation, was optioned to Triple-A Norfolk on Monday to put things back together. On Friday, he threw six scoreless innings, allowing three hits and striking out eight as the Tides beat the Charlotte Knights, 11-4.

"It's a double-edged sword. I want him to go down and work on things," Showalter said before Friday's game in Oakland.

Perhaps Arrieta's most impressive stat was the zero walks he issued. He threw 94 pitches, 54 for strikes.

"He knows he just can't throw his glove out there," Showalter said. "I'd like to see him carry the stuff he had up here."

Worth noting

• Baltimore leadoff hitters entered Friday leading the American League in on-base percentage, and the O's were one of just five teams whose leadoff hitters had walked more than they had struck out.

"You can't look at the leadoff position the same way it used to be," Showalter said. "You look for a guy with a little pop, a guy who take walks and a guy who steals bases. Rickey Henderson is in the Hall of Fame. There aren't many like him any more."

Rick Eymer is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.