Dancing With the Stars pro dancer Mark Ballas is allegedly "furious" about Julianne Hough's comments from Monday night's episode.

Hough was a guest judge on Monday's episode of Dancing With the Stars and criticized Ballas for showing off too much during his routines.

"The dancers were all talking about it," a source close to the show told Us Weekly this week. "Mark was so pissed after his routine, he was in silence, just gritting his teeth for a long time. He was so angry. Julianne is like his little sister he grew up with, and for her to make that dig at him - he felt like that was just so uncalled for."

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On Monday's show, Hough told Ballas' partner Christina Milian, "I've danced with Mark. You have to stand in front to make sure you're seen," suggesting that his choreography features himself more than his celebrity partner.

Ballas might have been especially hurt by Hough's comments considering his family trained her as a child. Ballas and Hough also participated in the Junior Olympics together.

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Ballas seemed taken aback by Hough's comments during the live show but did not voice any anger or resentment towards her.

"Mark kind of laughed off the remark when [fellow pro dancer] Derek [Hough] said something to him about it, but you could tell he was just angry and didn't want to talk about it," the source added. "He kind of brushed it off."

Ballas and Milian are among the final nine couples left in the competition.

Dancing With the Stars airs Mondays at 8 p.m. on ABC.

Watch Ballas and Milian's latest dance here, with Hough's comments included: