‘Dancing With The Stars’ Pro Emma Slater Catches Season 21 Contestant Hayes Grier's Fall During Rehearsals In Hilarious Video

dancing with the stars season 21 spoilers — Hayes Grier, 15, is putting his best foot forward during "Dancing With the Stars" rehearsals for the show's 21st season. Pictured: Grier at the premiere of Awesomeness TV's "Janoskians: Untold and Untrue" at the Bruin Theatre in Los Angeles, on Aug. 25, 2015. Getty Images

It looks like “Dancing With the Stars” pro Emma Slater and her Season 21 partner Hayes Grier have more to worry about than just what their team name should be. On Saturday, Slater, who will be partaking of her fifth on the hit ABC series, posted a sidesplitting video to her Instagram account showing her and the Vine star at rehearsals.

In the short video, Slater, 26, can be seen showing the 15-year-old contestant some tips on how to perfect a dance move.

“Straighten this,” she advises the second-youngest competitor in “DWTS” history on how to place his hands before critiquing his stance. But as the blond-haired dancer attempts to fix Grier’s feet, the wobbly social media star falls to the floor. The next thing Slater’s Instagram followers see is Willow Shields, who finished in seventh place during Season 16 of “DWTS,” laughing hysterically in the background.

Ok let's work on balance hayesgrier @willowshields @dancingabc https://t.co/4ro4svu0Q8
— Emma Slater (@EmmaSlaterDance) September 7, 2015

“The Hunger Games” star, who is the youngest celebrity to trip the light fantastic on the ballroom floor, attended Grier and Slater’s practice to give the youthful contestant some advice on competing. But hopefully the 15-year-old starlet also gave the green competitor some tips on how to, well ... stand!

Grier isn’t the only Season 21 contestant to have trouble staying on his feet. Bindi Irwin, the 17-year-old daughter of the late Steve Irwin, dished during an interview with Entertainment Tonight that she recently found herself laying facedown on the ballroom floor.

“[‘DWTS’] said, ‘We’re going to put you in these heels,’ and I don’t think they realized that I had never worn heels before,” said the crocodile-wrangling partner of Derek Hough, 30. "So I stood up and instantly fell down. Yeah, it was a good adventure.”

Fans can watch Grier and Irwin showcase their new dance skills during Season 21 of “Dancing With the Stars” when it premieres Monday, Sept. 14, on ABC.