It's time for that good old 'he said, she said' phase of Diddy and Cassie's breakup!

On Saturday (Dec. 29), Cassie debuted a new boyfriend on Instagram — just a couple of months after rumors swirled that she and Diddy had called it quits. Neither the mogul nor the model had ever confirmed the breakup, but this was all the confirmation one could need, and Diddy is calling a foul on the play!

In a report published by TMZ on Thursday (Jan. 3), Diddy's camp alleges that Cassie cheated on him with the new beau, Alex Fine. To add insult to injury, Fine was reportedly on Diddy's payroll as a trainer for Cassie.

According to the report, Diddy's personal trainer, Jamal Liggin, hired a team of trainers to assist him with Diddy and his crew. One of those trainers included Fine, who Diddy then assigned to Cassie for the last year. Sources told TMZ that the music mogul "feels betrayed," and is convinced that his longtime girlfriend was messing around with Fine while they were still dating. Cassie sources, however, insist that their relationship did not begin until after she and Diddy broke up. They did not specify when exactly it did begin, though.

It's been a rough couple of months for Diddy, who is still mourning the loss of Kim Porter, the mother of three of his children. He and Cassie briefly reconnected in the wake of her passing, but it appears that it was strictly for emotional support.

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