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Arizona Diamondbacks ace Zac Gallen had thrown 64 pitches through five innings on Friday night when he took the hill for the sixth. He ended up needing a visit from the team's trainer and left the game before throwing another pitch. It was unclear initially what the issue was. 

Later in the game, the Diamondbacks announced that Gallen had been removed due to right hamstring tightness. There's no word just yet as to the severity of the injury and we won't hear more about that for another day or two. 

On one hand, injuries to an ace are always bad news. On the other, this had nothing to do with a shoulder or elbow and from that perspective, the Diamondbacks and their fans can breathe a sigh of relief. It's always possible this is a minor hamstring thing, too, so it's within the realm of possibility that Gallen and the Diamondbacks dodged a bullet here. Again, we'll know more in a few days. 

Gallen is obviously a major piece for the Diamondbacks. He started the All-Star Game last season and was their postseason ace as they made a run to the World Series. He took a no-hitter deep into Game 5 of the World Series, too. Entering Friday, he'd pitched to a 3.00 ERA and 1.29 WHIP with 32 strikeouts in 27 innings. 

Arizona already has offseason signee Eduardo Rodríguez on the injured list along with frontline starter Merrill Kelly. Late spring signing Jordan Montgomery recently joined the rotation to alleviate some of the depth issues, but Kelly's injury made it a wash and now it's possible Gallen will join the IL, too. We'll see how he feels the rest the weekend. 

Other than Montgomery and Gallen, the rest of the remaining rotation right now includes Brandon Pfaadt, Tommy Henry and Slade Cecconi

The D-backs entered play Friday 12-14 on the year, good for a third-place tie in the NL West.