AceShowbiz -

After six months of dating, Kate Upton and Maksim Chmerkovskiy reportedly have called it quits. Work commitments apparently contributed to the split of the couple who was seen holding hands during a stroll in September.

"They are really good friends still and speak all the time, but their schedules just made it too difficult and it fell apart," a source told Us Weekly. "[Chmerkovskiy] has a lot of respect for her, but it just wasn't working anymore."

Another source, however, told E! News that the model and the former "Dancing with the Stars" pro did not really have serious relationship from the start. "It was never really that serious," the source said, calling Upton and Chmerkovskiy's relationship "more like friends-with-benefits than anything else."

"Things actually fizzled out between them in September. Maks moved to L.A. for his acting career and Kate relocated to NYC. After that, they actually didn't see very much of each other. There's no hard feelings, I'm sure they'll remain friendly," the source explained. Representatives for both Upton and Chmerkovskiy declined to comment.

The pair were first reported as an item in June. At that time, Chmerkovskiy and Upton were seen having dinner at Scalinatella in New York City to celebrate the Sports Illustrated cover girl's birthday. Later in October, Chmerkovskiy called Upton an "amazing person" in an interview.

He gushed, "We have an incredible time together, and, you know, I definitely didn't see that coming and I think neither did she. 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."