SAN FRANCISCO -- Right-hander Mason Tobin joined the competition for what's expected to be one, and only one, vacancy in the Giants' bullpen, signing a Minor League contract with an invitation to big league Spring Training.

Tobin has not pitched since April 2011 with the Texas Rangers. Receiving his first Major League action, he recorded a 6.75 ERA in four appearances before injuring his throwing elbow. Tobin then underwent Tommy John surgery for the second time.

Tobin's agent, Steve Canter, said Friday that the 25-year-old impressed Giants scouts during a workout earlier this month in Scottsdale, Ariz.

Except for that brief Major League stint, Tobin hasn't pitched above Class A. Formerly a starter, he went 6-4 with a 2.43 ERA in 25 outings (21 starts) in the Angels and Rangers organizations from 2007-09.

The Giants' other offseason acquisitions expected to contend for the relief role formerly held by Guillermo Mota include Scott Proctor, Fabio Castillo and Sandy Rosario. Holdovers and rookies also in the mix include Jake Dunning, Jean Machi and Dan Otero.