It was reported earlier this week that Santana had sustained another tear in the anterior capsule in his throwing shoulder. It's a similar injury to the one that caused him to miss the entire 2011 season.
When word of Santana's injury initially came out, there was speculation that he would call it a career rather than face another arduous rehab program. However, Santana's agent tweeted yesterday that his client planned on continuing his career.
This was apparently not an injury that occurred all at once, as it was termed "degenerative" by Dr. James Andrews. As such, it was something that happened over time, perhaps since he began rehabbing in 2011 following his initial surgery.
Over a year removed from his first significant shoulder surgery, Santana made 21 starts for the Mets last season. The 34-year-old maintained an ERA of 4.85 over 117 innings with a strikeout-to-walk ratio (SO/BB) of 2.85. From 2000-10 -- prior to surgery -- Santana posted an ERA of 3.10 with 3.55 SO/BB.