The Astros have placed right-hander Ryan Pressly on the 10-day injured list, amidst a series of roster moves. (MLB.com’s Brian McTaggart was among those to report the news.) Astros GM Jeff Luhnow told Chandler Rome of the Houston Chronicle and other media that Pressly will miss four-to-six weeks after undergoing arthroscopic knee surgery.

Infielder Jack Mayfield was optioned to Triple-A, while right-hander Joe Biagini was recalled from the minors and third baseman Abraham Toro’s contract has been selected for his Major League debut, as reported earlier today.

This is the second time that Pressly’s right knee has sent him to the IL this season, as he missed about two weeks in late July and early August due to soreness in the joint. The problem first arose when Pressly was hit in the knee by a ball off the bat of Andrelton Simmons back on July 18, and Luhnow said today that Pressly felt some more soreness after his latest outing. A previously-undiscovered “small issue” was found after a span of Pressly’s knee, and a surgical procedure seems to have been the decided course of action to fix the problem once and for all.

Luhnow is hopeful that Pressly will be able to return to action before the postseason begins, though the four-to-six timeline will make it a close call if Pressly’s recovery time is anything more than minimal. It also creates uncertainty as to whether Houston will have arguably its best bullpen arm fully healthy and ready to go come time for the playoffs.

Pressly’s dominant work earned him the first All-Star appearance of his seven-year career, as the righty has a 2.50 ERA, 11.6 K/9, 50.8% grounder rate, and 5.91 K/BB rate over 50 1/3 relief innings this season. Statcast credits him with the best curveball spin rate of any pitcher in baseball in 2019, and he is also in the 98th percentile of all pitchers in terms of fastball spin. It’s possible Pressly’s numbers could be even more dominant if it wasn’t for some bad luck with the long ball, as he has a 23.1% home run rate.

Losing Pressly is a big blow to any relief corps, even one as deep and talented as the Astros’ bullpen. Brad Peacock recently returned from the IL himself to add some extra depth, and Biagini will make a quick return after being optioned to Triple-A just last week. Aaron Sanchez is currently on the injured list recovering from a pec injury, though once he returns, he is also likely to lineup as a reliever in the postseason since Houston won’t need a fifth starter.

It also wouldn’t be surprising to see the Astros scour the waiver wire for any late pickups, or perhaps try to swing a trade with another team for a pitcher on a minor league contract (players on MLB deals can’t be traded after the July 31 deadline, of course). While Pressly’s loss isn’t likely to cost the Astros the AL West or anything, the team wants to have as many relief options as possible in preparation for what they hope is a long postseason run, especially if there’s any concern as to whether Pressly will make it back in time.