The A’s bullpen, which has developed into one of the top relief corps in baseball this season, took a hit on Thursday with the loss of right-hander J.B. Wendelken.

Wendelken was placed on the injured list prior to Thursday night’s three-game series finale against the Dodgers in Los Angeles. The A’s recalled James Kaprielian from their alternate training site to fill Wendelken’s spot on the active roster.

There was no specification as to why Wendelken was placed on the IL, and A’s manager Bob Melvin was unable to comment on the matter before Thursday’s game. It is important to note that being placed on the IL without further explanation is not confirmation that a player has tested positive for COVID-19. For example, potential exposure to a person who has the virus can be sufficient cause. So, too, are symptoms attributable to other illnesses, like a head cold.

Wendelken has been a key component to an A’s bullpen that entered Thursday leading the Major Leagues with a combined 2.43 ERA, elevating himself to a high-leverage role by posting a 1.80 ERA with 31 strikeouts over 25 innings.

Kaprielian, Oakland’s No. 11 prospect per MLB Pipeline, made his Major League debut in a relief appearance on Aug. 16 but has spent most of the season down at the club’s alternate site in San Jose. The 26-year-old right-hander is a starter by trade, though Melvin expects to utilize him out of the bullpen.

“The hard part right now is he hasn’t been able to throw to hitters since we’ve been on the road,” Melvin said. “These guys understand why they’re [at the alternate site] and have to take it seriously, because they could be called upon at any time.”