"Think of how many times he's been hit deep like that," he continued. "If it's a little higher, it's going to hit him in the head, so that's the most concerning thing about it."
Upton was hit in the back during the sixth inning on Monday night for his 15th hit-by-pitch of the year, which ranks third in the Major Leagues entering Tueday.
He was back in the lineup on Tuesday.
But there is something else that concerns Gibson about Upton getting hit.
"He's a very strong kid," Gibson said. "I'd hate to see him lose his mind and take matters into his own hands.
"I can tell you, if it was me, I couldn't guarantee what I would do at some point," he said. "I'm not promoting any kind of confrontation at all, trust me. But we've all probably lost our temperament sometime in our life. I hope it doesn't happen."