IBF featherweight champion the chance to appear on the Carl Frampton-Leo Santa Cruz bill in Las Vegas.
But Selby is eager to arrange another fight and revealed how Mares, the WBA 'regular' champion, swiftly offered to face him in Britain.
"I saw him at the weigh-in," Selby told Sky Sports. "He said 'let's do it'. I said 'listen, we can do it now,' and he made a joke about not bringing his shorts.
"That's a fight I would love and he said he was keen to come to the UK and fight me, so that's always a possibility."
Selby would endure a further setback as a discussed unification clash with Frampton appears to have been put back, with the Northern Irishman pushing for a third fight with Santa Cruz after losing his WBA 'super' title in a points defeat.
"I would have boxed and won, looked good," said Selby. "Frampton would have won and then that would have set up a unification fight for the summer back home.
"The worst case scenario was what happened. I didn't even fight and Frampton got beat. It's put things back a bit."
Instead of returning to the ring, Selby was a spectator at the MGM Grand, and found it hard to watch the Frampton-Santa Cruz rematch.
"That emotions going through me, I couldn't explain," he said. "I put something out on my social media and one guy said get over it, it's only a fight.
"To me, it's not a fight, it's my life. My life revolves around my children, my family, and boxing.
"If I'm not in the boxing gym, I'm in the house with my family. I don't go out, I don't party, don't drink or nothing. My life is boxing and my family."