Although Tillman's demotion was the news of the day -- giving the fifth starter spot to David Hernandez -- manager Dave Trembley also raved about the strides made by the left-handed Castillo.
"Castillo had a great camp," Trembley said. "I put Castillo in the category with a lot of the other guys who have shown a tremendous amount of improvement."
"It was very difficult to tell him [of the cut] because he feels like he can get people out, whether they are right-handed or left-handed, and I really can't argue with him."
A Cuban defect, Castillo was believed to be in direction contention with non-roster invitee Will Ohman for the team's lefty specialist role. In nine games, he allowed two earned runs, pitching to a 2.08 ERA with four strikeouts and no walks.
Catcher Adam Donachie and outfielder Jeff Salazar were also reassigned to Minor League camp. Baltimore will hang on to infielder Scott Moore and right-handed pitchers Alfredo Simon and Ross Wolf, although they have also been reassigned to Minor League camp. The trio will stay in Major League camp to provide depth.
"Simon betrayed common medicine," Trembley said. "He came back from Tommy John surgery [performed May 5, 2009] and was ready to go, Day One, in camp."
The 28-year-old Simon will get the start in Friday's game in Tampa, Fla., against the Yankees, and will report to Triple-A camp after that. Simon allowed five earned runs in five innings -- three of which came in his last appearance March 20 -- and strung together three straight scoreless outings prior to that.
"I think he will be up here at some point in time this year in some capacity," Trembley said of Simon.
The moves leave the Orioles with 33 players left in camp.