Cubs general manager Jed Hoyer said Thursday that Baez broke his thumb in celebration (via CSN Chicago):
"Celebratory high-five or (something like that)," general manager Jed Hoyer said Thursday. "They don't know exactly when he did it, but it was some sort of odd, non-baseball-playing injury. It certainly wasn't anything negative. He didn't punch a wall or anything. But it sounds like he was celebrating and might have hit it wrong."
Luckily for Chicago, there likely will not be any long-term concerns about Baez's injury. The 19-year-old is expected to be 100 percent by spring training.
Baez was selected No. 9 overall by Chicago in the 2011 draft. He made waves in Class-A Peoria, hitting .333 with a .979 OPS and 20 stolen bases in 57 games. His strong performance there earned him the No. 1 prospect ranking in the Midwest League from Baseball America.
Baez did struggle a bit when he was promoted to Class-A Daytona, and had not gotten off to the best start in Fall League. The infielder, who is a shortstop for now, will likely return to Daytona at the beginning of next season before getting promoted to Double-A Tennessee.