Watch video of Conor McGregor sparring with former boxing champ

Conor McGregor is working hard in the gym -- €” and to make us all believe he really might fight Floyd Mayweather Jr.

Both fighters have been feeding the rumor, despite UFC boss Dana White insisting the fight never will happen. And McGregor has been training with former IBF and IBO champion boxer Chris van Heerden, who's apparently a big fan of McGregor's boxing.

He's not the only one. Tony Jeffries, a former Olympic medalist and the co-owner of the LA gym where McGregor is sparring, appears to be impressed as well.