Last spring, all eyes were on the set of Bad Teacher — which reunited former flames Justin Timberlake and Cameron Diaz. (Timberlake, 30, was still involved with Jessica Biel at the time; they split last month.)

According to Diaz, it was anything but awkward or tense working with her ex on the dark comedy.

"No, it's great. Justin and I have always had a good laugh together, and to make a movie where we get to have a laugh together, and there really was no one else who was more perfect for this part," Diaz, 38, told UsMagazine.com at the Coliseum at Caesars Palace in Las Vegas Wednesday, where she was on hand to accept the CinemaCon Female Star of the Year Award.

She gushed that her ex (they parted ways in late 2006 after over 3 years together) is "a genius comedian. . . he's clearly talented. We went for the best person for the job, and it just so happened that it was him. And he delivers."

The "SexyBack" singer brings something to cinema that nobody else does, she enthused. "He's frickin' weird in movies. He's so bizarre and hilarious. I say that with great respect to his character and what he's done!"

Diaz, who is now hot and heavy with Yankees slugger Alex Rodriguez, continued to insist "there was nothing to make" of working with her ex. "[Just] two people who were working together, who just so happened to have gone out with one another at another time in our lives," said the star.

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"It really wasn't a big deal, we had a great time and did the job, and we do what all actors do afterward: We all go our separate ways. We'll all come back together for the premiere."

Another hot topic: The baseball player's girlfriend's amazing body. How does she do it? "Leg weights and weights and lifts, leg lifts — anything you can do on the floor. It's my horizontal workout," she explained.

As for food? "I need to eat every couple hours, so I’m just eating constantly, just to keep healthy," she explained. "I try to eat really clean. I eat a lot of protein, whether it's fish, chicken, or beef, or egg whites, and then brown rice or quinoa, and oatmeal and a whole grain like that, and lots of greens."

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