D-Backs manager Torey Lovullo said the injury is a "minor sprain of one section of his (ulnar collateral ligament)," according to Nick Piecoro of AZCentral. The team plans to have him rest for now, and they will "reassess" his elbow in a few weeks' time. Both the team and pitcher seem optimistic that it's not a serious issue.
"From my understanding, it sounds like surgery won't be needed," Gallen said, according to Zach Buchanan of The Athletic.
Gallen has continued to build on his breakout campaign last summer with a fine start to his 2021 season. The 25-year-old owns a 3.04 ERA, 2.99 FIP, and 1.20 WHIP while averaging 10.8 strikeouts per nine innings across five starts this year.
In addition to Gallen, the D-Backs also placed first baseman Christian Walker on the 10-day IL with an oblique injury.
Arizona selected right-hander Seth Frankoff and recalled infielder Andrew Young from Triple-A Reno as corresponding roster moves for Gallen and Walker. To make room for Frankoff on the 40-man roster, corner infielder Wyatt Mathisen was designated for assignment.