Belisario, 32, could compete for a spot in the Rays' bullpen this spring. The veteran right-hander went 4-8 with a 5.56 ERA and eight saves over 66 1/3 innings in 62 appearances for the White Sox last year. Belisario is 24-20 with a 3.75 ERA in 335 appearances over five seasons in the Majors.
With closer Jake McGee likely to start the season on the disabled list after undergoing arthroscopic surgery on his left elbow in December, Tampa Bay might have a spot or two up for grabs in the bullpen this spring.
Casilla, 30, has spent parts of nine seasons in the Majors with the Twins and Orioles. He has mostly played second base, but he's also seen time at shortstop and third base, so he could factor into the Rays' competition for a middle-infield spot this spring. Casilla is a career .247/.302/.331 hitter.
Adam Berry is a reporter for MLB.com. Follow him on Twitter at @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.