Kensing was a second-round Draft pick of the Marlins in 2003 out of Texas A&M and made his Major League debut as a 21-year-old in '04. He went 8-9 with a 5.23 ERA in 133 innings over 108 appearances with the Marlins over the next six seasons, including three starts.
The 6-foot, 190-pound Texas native pitched 26 games for the Nationals in 2009, when he was 1-1 with an 8.68 ERA in 28 innings before shoulder problems sidelined him for more than a year.
Kensing posted his best Minor League season last year with a 3.05 ERA in 44 relief appearances for Colorado Springs, the Rockies' top affiliate, with 37 hits, 41 strikeouts and 22 walks in 44 1/3 innings.
Pina, 26, has split his professional career in the Rangers' and Royals' organizations. He played five Major League games with the Royals in 2011 and '12, going 3-for-16 (.188) with two doubles in his brief stints.
Pina spent last season with Double-A Northwest Arkansas and Triple-A Omaha in the Royals' system, hitting a combined .228 with seven home runs and 38 RBIs. He threw out 32 of 79 attempted basestealers (40.5 percent).
The 6-foot, 215-pound Venezuelan was originally with the Rangers as a non-drafted free agent in 2004.
Pina gives the Mariners added depth at catcher, where they've also recently signed veteran free agent John Buck to a Major League deal and Humberto Quintero to a Minor League contract with a Spring Training invitation.
Mike Zunino, Jesus Sucre and Buck are the only catchers on the 40-man roster, with Jesus Montero converting to first base. But Pina, Quintero and Minor Leaguers John Hicks and Michael Dowd will join that group when pitchers and catchers report to Peoria, Ariz., on Feb. 12.
The Mariners' Spring Training roster is currently at 61 players, including 30 pitchers and the seven catchers.
The first workout for pitchers and catchers will be Feb. 13, with position players reporting Feb. 17 and the first full-squad workout following on Feb. 18.