According to Jenifer Langosh, both Yadier Molina and Randal Grichuk underwent surgery for various ailments.
Yadier Molina had to have a second thumb ligament surgery yesterday. The first didn't take. That'll keep him out for most of ST. #stlcards— Jenifer Langosch (@LangoschMLB) December 16, 2015
In other #stlcards medical news: Randal Grichuk had sports hernia surgery. He's expected to be fully ready at start if Spring Training.— Jenifer Langosch (@LangoschMLB) December 16, 2015
The report on Grichuk isn't concerning, and he should be fine heading into 2016. St. Louis is counting on a repeat performance from Grichuk (.276/.329/.548 with a wOBA of .370 and a wRC+ OF 137 in 350 PA's), especially since they missed out on Jason Heyward in free agency.
The more troubling news is undoubtedly surrounding Molina, as he might not be ready for the start of the 2016 season now. Fortunately for the Cardinals, they signed Brayan Pena earlier this offseason, who should be able to fill in for Molina without any major issues.
In 367 PA's last season with the Reds, Pena hit .273/.334/.324, with a wOBA of .295 and a wRC+ of 82. While Pena likely won't provide a huge offensive boost, his statistics were fairly similar to Molina's line of .270/.310/.350, with a wOBA of .287 and a wRC+ of 80.
As of now, it's unclear what Molina's timetable is, but the Cardinals will need to keep a close eye on him as the third catcher listed on their 40-man (Mike Ohlman) roster hasn't played above AA.