Lynn, 28, went 12-11 with a 3.03 ERA (131 ERA+) in 31 starts and 175 1/3 innings in 2015. He battled forearm and ankle trouble during the season. Lynn signed a three-year contract worth $22 million last offseason, so he doesn't have to worry about the procedure hurting future arbitration salaries.
Here are three other things to know about Lynn's elbow injury and its impact on the Cardinals.
1. The Cardinals have a lot of health concerns in their rotation.
Lynn will not pitch at all next season. We know that now. This past season the Cardinals were also without Adam Wainwright for most of the year due to a torn Achilles. Carlos Martinez had to be shut down in September due to a shoulder strain. Michael Wacha didn't get hurt -- he had a stress fracture in his shoulder in 2013 -- but was clearly worn late in the season.
Jaime Garcia? He made 20 starts in 2015 after making 16 starts total from 2013-14. He's battled all sorts of arm injuries in recent years and was finally able to get back on the mound for a significant period of time this summer. Garcia pitched so well (163 ERA+) the Cardinals exercised his $11.5 million option after the season. At this time last year the option decision was very much in doubt.
Wainwright, Garcia, Wacha and Martinez figure to be four of the team's five starters next season, and all four come with health concerns. It might work out, but that's not a good situation.
2. The Cardinals need to add a starter this offseason, if not two.
Thanks to the questionable rotation health outlined above, the Cardinals are going to have to add a starting pitcher this offseason. At the very least they need to re-sign or replace free agent John Lackey, who gave the team 218 innings with a 143 ERA+ in 2015.
St. Louis has Tyler Lyons, Tim Cooney and Marco Gonzales as depth pitchers, but adding another veteran innings eater would be a wise move. Heck, signing two wouldn't be a bad idea, not with Martinez coming off his shoulder injury and Wacha looking so taxed in September and October. There's no such thing as too much pitching.
Obviously Zack Greinke and David Price are the big names. If the Cardinals don't want to break the bank -- they already have a bonafide ace in Wainwright, after all -- second-tier free-agent starters like Bartolo Colon, Doug Fister, J.A. Happ and Chris Young could be lower cost options. There's always potential trades as well.
3. Lynn had the surgery at the best possible time.
Tommy John surgery is obviously very bad and the Cardinals will be worse without Lynn next season. That said, he had the procedure at the best possible time. First and foremost, he's now guaranteed a full 15-month rehab before spring training 2017. There won't be any temptation to rush him back in 12 or 13 months.
Secondly, it's very early in the offseason. The only notable transaction so far is the Nathan Karns-Brad Miller trade. Every free-agent starter remains on the board. The Cardinals have time to digest the Lynn injury, develop a plan of attack for the coming weeks, and execute it. This is the best of an otherwise bad situation.