Justin Upton missed Tuesday night's game against the Pirates, as the Diamondbacks have elected to sit him due to a thumb injury he suffered in the team's Opening Weekend series against the Giants.

Upton, who is hitting just .212 with 0 home runs and 0 RBI, has struggled mightily.

"He's not swinging the bat well," Gibson said. "I think it hurts him. He's trying to fight his way through it. He slid the other night, and he pounded it again. You get jammed when [the ball] hits the bat a certain way."

Tweeted Diamondbacks beat writer Nick Piecoro:

Dbacks are taking today to reevaluate Justin Upton's thumb. He's seeing a hand specialist, probably getting an MRI, Kirk Gibson says.

— Nick Piecoro (@nickpiecoro) April 17, 2012

Upton's health is of the utmost importance to the D-backs, though if there is one position they could somewhat afford to lose someone at it's in the outfield, where Gold Glove winner Gerardo Parra can step in and play every day.

Gibson will be cautious in handling his All-Star right fielder's return and isn't ruling out a stint on the disabled list.

"It could be, I don't know," manager Kirk Gibson said. "At some point you have to think long-term. If he's keeps beating on it, it's not going to get better. Then, that's something we would probably consider.

That said, the Diamondbacks would certainly love to get Upton, an All-Star in 2011 and MVP candidate, back healthy and in the lineup as soon as possible.