The team also optioned infielders Jonathan Schoop and Yamaico Navarro to Triple-A and reassigned right-hander Daniel McCutchen to minor league camp. Those moves trim the Orioles' spring roster to 40 players.
"He's just got some people ahead of him right now, simple as that," Orioles manager Buck Showalter said. "He has the potential to change that. At the major league level, it's about people who consistently give you a chance to win the game, and Zach's capable of doing [that].
"He knows he's not quite where he needs to be. I have confidence he'll get there."
In his last outing Wednesday, Britton allowed five runs and seven hits in 1 2/3 innings. That all but killed his chance at a rotation spot, especially with leading candidates Jake Arrieta and Brian Matusz both pitching well.
"It's disappointing, but I think you understand that it's a fierce competition and guys have thrown better than me, plain and simple," Britton said. "I have some things that I need to get better at. Coming off that injury last year, I still feel like there are adjustments that need to be made, and it's easier to do that down there than at the big league level, especially [because] we want to win right off the bat."
With Britton likely out of the rotation mix, at least barring any drastic changes between now and the beginning of the season, the spot comes down to Arrieta, Matusz, Steve Johnson, nonroster player Jair Jurrjens and Rule 5 pick T.J. McFarland.
Britton said the team told him to work on the arm slot of his sinker, which is his best pitch, for more consistency. Britton, who didn't pitch in a game last spring due to a left shoulder impingement and began in Triple-A, said he struggled to throw the sinker effectively last year because of the injury.
"I'm getting to that age where you have to start putting some consistency together," Britton said. "With where the options are with me right now, it's definitely, 'Hey figure it out,' let's get consistent, so I can stick in the big leagues from now on and not go through the up-and-down process anymore."