Fielder announced last summer that he can no longer play baseball after undergoing a second operation on a herniated disk in his neck, but he is signed through 2020. He had to be kept on the 40-man roster during the winter and will spend the season on the 60-day DL. The Rangers now have 39 on their 40-man roster.
That leaves room for free-agent first baseman Mike Napoli, who agreed to a one-year deal with an option for 2018. That deal has not been officially announced pending a physical, which should take place in the next day or two.
Gamboa made his Major League debut for the Rays last season and went 0-2 with a 1.35 ERA. He allowed nine hits and eight walks in 13 1/3 innings while striking out 11. He threw his knuckleball 70.3 percent of the time.
Gamboa was a 21st-round pick by the Orioles in 2008 out of UC-Davis. He rose through the Orioles system on conventional stuff but couldn't get past Double-A. In Spring Training of 2013, he started throwing a knuckleball after Hall of Famer Phil Niekro visited camp to work with another pitcher.
Gamboa left the Orioles after the 2015 season and signed a Minor League contract with the Rays. He spent most of last season with Triple-A Durham and went 6-4 with a 2.68 ERA in 12 starts and 15 relief appearances.
T.R. Sullivan has covered the Rangers since 1989, and for MLB.com since 2006. Follow him on Twitter @Sullivan_Ranger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.