The O's designated Tolliver for assignment when they added lefty Kyle Lobstein on Wednesday. Lobstein, who was designated hours after he was added due to the acquisition of outfielder Drew Stubbs, cleared waivers and was outrighted to Triple-A.
The 28-year-old Tolliver made his MLB debut this season, and gave up four runs (three earned) in 4 2/3 innings of relief over five games.
Showalter said the O's discussed Lobstein's future Saturday, and the plan is to send him to the club's spring complex in Sarasota, Fla., when the regular season ends, "just in case" the O's need postseason pitching help.
Brittany Ghiroli has covered the Orioles for MLB.com since 2010. Read her blog, Britt's Bird Watch, follow her on Facebook and Twitter @britt_ghiroli, and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.