The rest of the bullpen will be Carlos Marmol, Kerry Wood, James Russell and recent acquisition Shawn Camp. Russell is the only left-hander, and general manager Jed Hoyer said they are on the lookout for another one.
"Ideally, we would've been able to find another lefty," Hoyer said Wednesday. "We haven't matched up yet. I think it's safe to say it's something we'll be looking to do during the first part of the season to try to find another lefty. Russell is a very good left-hander, but having two would make life easier for Dale [Sveum]."
Castillo, 22, was selected last December in the Rule 5 Draft from the Phillies, and the converted shortstop will be making the jump from Class A to the big leagues. This spring, the right-hander appeared in 11 games, giving up five earned runs on 12 hits and 10 walks over 13 innings.
Dolis, 24, was charged with one run on three hits and six walks over 10 innings in nine Cactus League games. He spent last season at Double-A Tennessee, where he was 8-5 with a 3.22 ERA in 51 games, including four starts.
Camp was claimed off waivers from the Blue Jays this spring. He appeared in 11 games total, and gave up five runs on 16 hits and five walks over 14 1/3 innings.
Rodrigo Lopez was in Chicago for Wednesday's workout and projected as the long man in the bullpen, but he will not be on the Opening Day roster.