Three-division titlewinner Abner Mares has begun training with Virgil Hunter, Golden Boy CEO Richard Schaefer informed RingTV.com on Tuesday.

Mares (26-1-1, 14 knockouts) was being considered for the June 21 Showtime card at the StubHub Center in Carson, Calif., that features the Gary Russell Jr.-Vasyl Lomachenko WBO featherweight title bout, as well as former welterweight titleholders Robert Guerrero and Devon Alexander in separate bouts against Yoshihiro Kamegai and Jesus Soto Karass, respectively.

"I was informed that he recently made a shift in trainer to Virgil Hunter, and, so he wants to make sure that he has enough time to properly prepare to train," said Schaefer. "June 21 is only about six weeks away, so it was just a bit too much of a rush, he wants to make sure that when he makes his comeback, that he's properly prepared."

Mares, 28, was last in action in August, when he lost his WBC featherweight title after suffering a shocking first-round knockout loss to Jhonny Gonzalez. Mares later suffered a rib injury in Mexico City that scuttled his rematch with Gonzalez that was slated for February.

Mares was similarly injured in June 2012, when rib damage led to the cancelation of a clash with bantamweight Christian Esquivel.

Managed by Frank Espinoza, Mares was THE RING's No. 5-rated pound-for-pound fighter entering the bout with Gonzalez. He was floored twice by the Mexican veteran during the first defense of the belt he won in his 126-pound debut, a ninth-round knockout of Daniel Ponce de Leon.

Ponce de Leon was the last man to defeat Gonzalez in an eighth-round technical decision in September 2012, ending Gonzalez's 12-fight winning streak which included 11 knockouts.