According to McTaggart, Correa told reporters he experienced trouble breathing during games this season, which led him to elect for the surgery.
The 24-year-old missed 53 games in 2017, in large part due to a torn ligament in his left thumb. Another injury—albeit more minor—hampered the 2017 All-Star in June when the Astros placed him on the 10-day disabled list with back stiffness.
The issue could partly explain why Correa's performance declined slightly. Despite missing so much time, he was third among shortstops in WAR (5.2), per FanGraphs. He finished 22nd at the position in 2018 with 1.6 WAR. Correa batted .239 and slugged .405 while posting 15 home runs and 65 RBI.
Based on McTaggart's report, Correa's breathing problems could also have led to his struggles at the plate.
As long as he stays healthy, the 2019 season could see Correa return to an All-Star level.