Santana reportedly had been pitching in the Venezuelan Winter League but was forced to miss the rest of the season after feeling stiffness in his shoulder. He last pitched in MLB with the New York Mets in 2012 and threw the franchise's first no-hitter in June of that year.
Santana, 34, has undergone two major shoulder surgeries, the last of which took place in April 2013.
Santana agreed to a one year, minor league contract with the Baltimore Orioles last March, but he did not pitch in the majors after he tore his Achilles tendon in June. Santana spent the first eight seasons of his career with the Minnesota Twins before signing a six-year, $137.5 million deal with the New York Mets in 2008.
He won Cy Young awards in 2004 and 2006 and has earned four All-Star nods. Over 12 major league seasons, Santana has recorded a 3.20 ERA with 1,988 strikeouts and 567 walks.