He says I'm the only one, but my friends say he's playing the field.

I know you got charm and appeal / You always play the field / I'm crazy to think you're all mine

In a world where you can get a sexual partner faster than a pizza delivery, it has never been easier to play the field.

But ostriches in breeding season are relentlessly promiscuous, with both males and females seeking liaisons with multiple partners. No doubt they have their reasons. But from an evolutionary perspective, playing the field is a way to get diverse DNA into as many nests as possible and compensate for the fact that most nests fail.

Play the field

Meaning

Verb