Ben Affleck and Jennifer Lopez
Ben Affleck and Jennifer Lopez called off their engagement in 2004 Reuters

Ben Affleck is unhappy that Jennifer Lopez is dating former baseball star Alex Rodriguez. The Argo star is upset over the fact that the singer's new love is a former New York Yankees player.

A source told Hollywood Life: "Everyone knows that Ben is the number one Boston Red Sox fan. He is still friendly with Jen to this day and he is hating that she is with someone so tied to the New York Yankees. He can't wait to bust her balls about it when they see each other again at an award show or outing."

"As much as he will joke about it to her, he secretly hates that she chose A-Rod, the worst Yankees player in his mind," the insider added.

"When it comes to love she marches to the beat of her own drum, and she can't help being a hopeless romantic. Friends are worried because she's only just come out of the relationship with Drake and she's jumped right back in. There's concerns that she's moving way too fast," the source said.

Affleck and Lopez dated for two years, but called off their engagement in 2004. The Oscar winner had previously revealed he is in good terms with Lopez despite the split. He told The Hollywood Reporter: "We do have the kind of relationship where there'll be an email saying, 'Oh, your movie looks great.'"

"I remember when she got American Idol. I said, 'This was really smart. Good luck.' I touch base. I respect her. I like her. She's put up with some stuff that was unfair in her life, and I'm really pleased to see her successful," he added.