LAKELAND, Fla. -- The Tigers' bullpen competition was reduced by three players on Sunday. Detroit optioned right-hander Freddy Dolsi to Triple-A Toledo while assigning left-hander Fu-Te Ni and righty Casey Fien to Minor League camp.

All three are expected to be part of the bullpen with the Mud Hens, with a chance to rejoin the Tigers as the season goes along. Detroit, meanwhile, heads into the final couple of weeks of Spring Training with a few spots still open and a few potential candidates to compete for them.

Fien had put together an impressive camp for the Tigers, reinforcing his reputation as a strike thrower with 7 1/3 innings of one-run ball. However, the 25-year-old had just 12 appearances above Double-A last year, accumulating less experience than many of the club's other bullpen candidates.

"The only thing that he needs to do to get to the big leagues -- actually pretty quick, I think -- is refine his breaking ball a little bit," manager Jim Leyland said. "He'll be a big league pitcher no matter what, probably, but he'll have more success if he gets a little better breaking ball."

By contrast, the 26-year-old Dolsi spent a good portion of last season in the Tigers' bullpen, making 42 appearances across 47 2/3 innings with Detroit while allowing just three home runs. But his 28 walks reflected a battle with command. Dolsi walked only one batter over 7 2/3 spring innings, including a perfect ninth inning for a save against Team Venezuela in a March 2 exhibition. He allowed four hits, however, in each of his past two appearances, resulting in three earned runs.

Ni was expected to start the season in the Minor Leagues after signing with the organization from the Chinese Professional Baseball League during the offseason. Still, the 26-year-old left a good first impression with his funky delivery and deceptiveness. He tossed scoreless innings in each of his first three appearances before allowing two runs on three hits in two-thirds of an inning on Friday against the Nationals.

The moves leave 42 players still in camp, including 19 pitchers. How many will compete for relief spots in the end will depend in part on the fifth-starter competition, but the list of remaining relievers includes several non-roster invitees, from veterans Juan Rincon and Scott Williamson to former first-round Draft pick Ryan Perry and former Minor League Rule 5 Draft pick Eddie Bonine. Right-hander Alfredo Figaro also remains with an impressive camp so far, as do left-handers Clay Rapada and Kyle Bloom.