Trembley said before Tuesday night's game against the Seattle Mariners that he thinks Baltimore's best starter in 2009 will be back in the Orioles rotation "soon."
Baltimore recalled Alberto Castillo from Norfolk and put the left-hander in an overworked bullpen for Tuesday's game.
The Orioles don't need a fifth starter again until May 1 because of two off days. Trembley says the team will go with four starters until then.
Bergesen has started his second major league season 0-2 with a 12.19 ERA through three starts. He lasted only 2 2/3 innings Monday and allowed six hits and seven runs -- four earned -- in an 8-2 loss to the Mariners.
He was 7-5 last year in 19 starts. His 3.43 ERA was second among AL rookies.