Maksim Chmerkovskiy may be on the outs with supermodel Kate Upton.

After Upton was spotted attending a New York Knicks basketball game with a mystery man, an insider revealed the couple's future plans to attend a wedding together have been scrapped.

"Maks isn't saying anything bad about her, but it's a very telling development that she's no longer accompanying him to the wedding," an alleged source told Radar Online.

The pair--who was first spotted together on a date in June--has not been seen together in public since Oct. 28. The VOGUE cover model was also with another man at an NBA game at Madison Square Garden in New York City on Nov. 16.

"Maks has been telling friends that he is no longer bring Kate to a wedding that they were both scheduled to attend together," added the insider.

Kate Upton New Bikini PHOTOS; Twitter Posts from 'The Other Woman' Exotic Location 

The pair was first spotted together on a date in June. When the dance pro was questioned about holding hands with Upton in public, his rep told Life & Style Weekly at the time that their relationship was platonic. They were seen together again on a shopping trip at the Gucci boutique on Fifth Avenue in New York City on Sept. 18. Chmerkovskiy was reportedly affectionate with the magazine cover girl.

Kate Upton and Maksim Chmerkovskiy Dating, 'Dancing With the Stars' Pro Says He's 'Lucky Guy'

When the 33-year-old dancer went public about their relationship in October, he described her as "an amazing person." He also admitted that their budding friendship took him by surprise.

"We have an incredible time together, and, you know, I definitely didn't see that coming and I think neither did she," Chmerkovskiy told Us Weekly. "We enjoy each other's company very much and like I said, she's a great girl that I never thought anything romantic like this could have happened."