Zac Gallen injury: D-backs ace exits start vs. Mets after six pitches due to hamstring strain

Already facing an uphill climb in the standings, the Arizona Diamondbacks lost ace Zac Gallen to a hamstring injury Thursday night. Gallen exited his start against the New York Mets at Citi Field (NY 3, ARI 2) with a right hamstring strain after only six pitches, the team announced. He will have tests Friday to determine the severity of the injury, manager Torey Lovullo said (via MLB.com).

Here is Gallen’s injury. There’s not much too it — he threw a pitch and came up favoring his leg. He didn’t throw a test pitch, instead immediately leaving the game with the trainer. Gallen had a slight limp as he exited the field.

Gallen exited his April 26 start against the Seattle Mariners with tightness in the same hamstring. The D-Backs did not place him on the injured list. They used scheduled off-days to skip Gallen’s next start and give him 10 days off before his next outing. He returned May 7 and has pitched well since, and had reported no issues with his hamstring.

The D-Backs are already without Eduardo Rodriguez, their big free agent signing, and the reliable Merrill Kelly. Rodriguez has a lat strain and Kelly has a shoulder issue. Both are on the 60-day injured list and are weeks away from returning. Losing Gallen for any length of time would be a significant blow to a team pushing the limits of its pitching depth.

Arizona’s rotation depth chart looks like this at the moment:

1. RHP Zac Gallen (exited Thursday’s start with a hamstring strain)
2. LHP Jordan Montgomery
3. RHP Merrill Kelly (out with shoulder injury)
4. LHP Eduardo Rodriguez (out with lat injury)
5. RHP Brandon Pfaadt
6. RHP Ryne Nelson
7. LHP Blake Walston
8. LHP Tommy Henry
9. RHP Slade Cecconi

Cecconi, Henry, and Nelson have combined for a 5.93 ERA in 19 starts this season. Even Montgomery, who signed during the final week of spring training, has struggled. He has a 4.69 ERA in seven starts. Walston made his MLB debut earlier this month and held an admitted weak Miami Marlins offense scoreless in 4 2/3 innings in his first start last weekend. 

Even with Corbin Carroll’s season-long slump, the D-Backs are averaging 4.51 runs per game, ninth most in baseball. Keeping runs off the board has been challenge though. Arizona is allowing 4.58 runs per game, 10th most in baseball. Now they could lose Gallen, who has 3.12 ERA and averages close to six innings per start, to a hamstring injury.

Thursday’s loss dropped the D-Backs to 25-31 this season. They are 5-2 against the very bad Colorado Rockies and 20-29 against everyone else. Arizona is 3.5 games back of the third wild-card spot with five teams ahead of them.