The Diamondbacks announced that Iannetta received stitches in his upper lip and suffered a couple fractured teeth and a nose fracture.
Leading off the seventh inning against the Pittsburgh Pirates, Iannetta appeared to turn into the pitch, a 93 mph fastball from reliever Johnny Barbato.
Iannetta remained facedown in the dirt for several minutes, and blood was dripping off his face as trainers attended to him. He was able to walk off the field with help, holding a cloth to his face.
Diamondbacks manager Torey Lovullo said he thought the pitch that hit Iannetta "just got away from their pitcher. I'll stand by that."
The Associated Press contributed to this report.