It's not good, but it could have been much worse. Thankfully, he had his helmet on. He still got his head cut open.
update:
Brewers manager Ron Roenicke updated reporters on Segura's status after the game.
"No concussion, no fracture but he was laid open pretty good. So a plastic surgeon stitched him up," Roenicke said. "He'll have some swelling tomorrow, I'm sure, so we'll see how quickly it goes down and how many days (out of the lineup) it's going to be."
http://espn.go.com/mlb/story/_/id/10845163/jean-segura-milwaukee-brewers-leaves-game-getting-hit-teammate-ryan-braun-bat