Ever since Johan Santana suffered a re-tear of his anterior capsule in his left shoulder back in spring training, Mets fans have assumed that his days wearing a Mets uniform were over. Signed to a six-year, $137.5 million contract following his blockbuster trade from the Twins in February 2008, Santana has had his share of ups and downs in a Mets uniform. His contract includes a $25 million club option with a $5.5 million buyout that the club will certainly be exercising. Even though Santana will be a free agent now that the World Series is over, GM Sandy Alderson has stated that a return for Santana isn't out of the question.
Santana pitched well over the course of his six-year tenure with the team, pitching to a 3.13 ERA while compiling impressive strikeout and walk rates, at 7.6 and 2.5 per nine innings, respectively. However, performance wasn't as much an issue for Santana during his time with the team as health was. His overall numbers only included four of six seasons, as he missed two out of the last three seasons due to the same tear of the anterior capsule in his left shoulder. Additionally, he was only able to complete one full season with the Mets out of all six (granted, he did fire 199 innings and pitched into September in 2010) and was either shut down for the entire season or the remainder of one due to a variety of injuries in the last five straight seasons. And in the last season he actually threw a pitch, 2012, he had a 4.85 ERA over just 117 innings. Things started to go downhill for him in 2012 directly after—but not necessarily as a result of— this magical moment.
In the end, Alderson probably thinks of Santana in the same mold as Chris Young, Chris Capuano, and Shaun Marcum: established pitchers with injury histories who are looking to re-establish themselves on a one-year deal. However, given the uniqueness of Santana's injuries—no major leaguer has ever undergone two surgeries for the same tear of the anterior capsule—Alderson probably won't offer Santana a contract similar to Capuano's and Marcum's (who received major league deals) and will instead offer a contract of the minor league variety like he did for Chris Young (who also suffered a tear of the anterior capsule).
The cost would be minor, if Santana is willing to forgo a major league contract. Given both his laundry list of injuries and the uniqueness of some of them, a minor league contract is exactly what should be offered to Santana. However, there are 29 other MLB teams and all it takes is for one to offer him a major league guarantee. It is also possible that no other team offers him a deal that is financially better than any that the Mets could offer but that Santana simply decides that after six up-and-down seasons, a change of scenery is necessary. Therefore, it seems that the question is not so much the cost as it is Santana's desires.
The fit is obvious. The Mets need starting pitchers and Santana pitches, or at least tries to do so. If he were to sign a minor league deal and earn a spot in the rotation, he could easily slide in as the team's fourth starter behind Jon Niese, Dillon Gee, and Zack Wheeler. Moreover, if he were to sign a minor league deal with the team and actually had to spend some time in the minors, he could still be a very valuable piece given his ability to mentor some of the team's younger arms, including Noah Syndergaard and Rafael Montero.