"Realistically, it's eight weeks," Gibson told reporters before Sunday's game against the Pittsburgh Pirates. "So he's done."
Goldschmidt, runner-up in National League MVP voting last season, was hurt when he was hit by a pitch from Ernesto Frieri in the ninth inning of Friday night's loss to the Pirates. The Diamondbacks placed Goldschmidt on the 15-day disabled list.
Pirates outfielder and reigning NL MVP Andrew McCutchen was hit by a Randall Delgado pitch squarely in the lower middle of his back in the ninth inning Saturday night with his team up by four runs and runners on second and third.
"Sure it did," McCutchen said with a hint of sarcasm when told that Gibson said the pitch from Delgado got away from him. "They had all game to retaliate. They had the first inning to retaliate. They had the first pitch [of the ninth inning at-bat] to retaliate. They missed. You throw a slider on the second pitch and then you throw up and in on the next pitch. Are you trying to hurt me too? That's the question.
"We understand that retaliation is going to happen in this game. But you know, there's a right way to do it," McCutchen added. "If you're going to hit me, hit me. He hit me square in the spine. If I get hurt, what happens then?"
While Diamondbacks catcher Miguel Montero called the situation Friday "a little shady," Goldschmidt said after the game he didn't think he was hit purposely.
"Guys have to try and get outs," he said. " What do you want them to do? Just throw it down the middle? They pitch inside as a team. We do it too. We want our pitchers to be able to pitch inside. You don't want to see anyone get hurt but sometimes it may or may not happen."
The Pirates enter Sunday's series finale trailing the Milwaukee Brewers by 1½ games in the NL Central standings.
The Associated Press contributed to this report.