Smith injured his hand punching something in frustration after allowing two runs and three hits in two innings of relief against Atlanta on Saturday. The injury occurred after he was removed from the game.
"Caleb broke his hand by punching something that he shouldn't have been punching," Arizona manager Torey Lovullo said. "I don't know exactly what it was, but he was very frustrated when he came out of the game."
Lovullo has expressed his displeasure about the incident to Smith, who returned to Arizona, where the steps in his rehab process will be determined.
"I had a conversation with him and shared my frustration," Lovullo said. "He's been accountable to that. He shares the same frustration that I do and his teammates do. He's been throwing the ball really well."
Lovullo doesn't know if Smith will have surgery or how long he'll be sidelined.
"The one tiny, tiny piece that's a silver lining, it's his right hand and he can still throw a baseball," Lovullo said. "Once he's cleared for full baseball activity, it's not going to be a huge ramp up to get his arm back in shape. And that's a small silver lining."
Smith is 1-1 with a 4.66 ERA in 31 appearances.