Johnson will replace left-hander Brian Matusz on the 25-man roster. Matusz was optioned after today's 6-2 loss to the Indians at Camden Yards.
Johnson, 24, is 3-5 with a 2.73 ERA in 14 games, including nine starts. He's allowed 43 hits, walked 24 and struck out 63 in 62 2/3 innings, and opponents are batting .194 against him.
The St. Paul's graduate was invited to spring training this year. The Orioles placed him on the 40-man roster on June 3 before he chose to opt out of his contract and become a free agent. He was moved to the bullpen because the Tides were overloaded with starters, including 49-year-old Jamie Moyer, who recently was granted his release and signed with the Blue Jays.
Johnson pitched two innings in relief yesterday and would most likely be available tonight. He's 2-0 with a 0.53 ERA in five games since moving to the bullpen, with one earned run (three total) and eight hits allowed, 10 walks and 24 strikeouts in 17 innings. He tossed five scoreless and hitless innings against Columbus on June 26, with two walks and eight strikeouts.
This will be the first major league experience for Johnson, whose father, Dave, pitched for the Orioles from 1989-1991. The Orioles acquired him from the Dodgers along with third baseman Josh Bell on July 30, 2009 in exchange for reliever George Sherrill.
The Orioles still could recall a starter for Friday's game in Anaheim when Matusz's turn comes up. Zach Britton is pitching tonight for the Tides and would be working on normal rest. Chris Tillman is another possibility.
Executive vice president Dan Duquette told reporters today that Miguel Gonzalez wasn't being considered for the assignment.
Update: Britton allowed two runs (one earned) and three hits in six innings, with four walks and seven strikeouts. He threw 107 pitches, 63 for strikes.
J.C. Romero retired the final batter to record his second save.
Romero has an opt-out clause in his contract and the Orioles must make a decision on him at the All-Star break. Romero left the Tides briefly and was placed on the temporary inactive list before coming back. It appears that he's losing patience with his situation and wants a promotion or the chance to find another job.
Eric Beaulac, who appeared in four games with Single-A Delmarva this year, relieved Britton today and picked up the win in his Norfolk debut.
The Orioles also need a starter on Thursday unless they're keeping Dana Eveland in the rotation. Eveland started yesterday's game against the Indians.