Maksim Chmerkovskiy is sitting out Monday's Dancing With the Stars performance.
The 37-year-old pro dancer suffered a calf injury during rehearsals with his partner, Glee star Heather Morris. As a result, troupe dancer Alan Bersten will take Chmerkovskiy's place on Monday's show. In video of the injury, Chmerkovskiy gives an audible cry of pain in the middle of a fast-paced dance, and says "something went down."
"It's my calf muscle," he says. "It just felt like something hit it. I can't stand on it. It's not good."
WATCH: EXCLUSIVE: Maksim Chmerkovskiy Praises Peta Murgatroyd for Returning to 'DWTS' 2 Months After Giving Birth
Chmerkovskiy also Instagrammed the news, sharing a picture of him and 30-year-old Morris hugging.
"Sorry I was MIA. Tune in to @dancingabc today and all will be explained," he wrote. "Tough show for #teamMaksimumHeat and @heatherrelizabethh would have to hold it down for both of us. Please show her your love and support while I work on getting my ass back to the ballroom. #DidNotSeeThisComing #WillBeBackBetterThanEver."
It is unknown when Chmerkovskiy will return to the stage.
Morris and Chmerkovskiy have emerged as one of this season's big front-runners, getting a score of 28 out of 40 for their performance last week, a Viennese Waltz to "Make Something Beautiful" by Ben Rector.
WATCH: 'Dancing With the Stars' Biggest Ballroom Bombshells -- Engagements, Baby Announcements, Feuds and More!
ET spoke to the pair earlier this month, when Chmerkovskiy admitted just how bad he wants this season's mirror ball trophy.
"I got a mantle at home, it has two of [my brother] Val [Chmerkovskiy's] mirror balls, it has two of [my fiancee] Peta [Murgatroyd's] mirror balls, it even has a little mirror ball for the baby, and my lonesome mirror ball by itself," he explained. "It's feeling insecure and needs company, for sure," he confessed. "I just need to get balls evened out, and this is the opportunity. I'm not gonna stop."