DENVER — The anticipated return of a key Mets reliever has been placed on hold.  A.J. Minter is dealing with left hip discomfort, according to manager Carlos Mendoza, and has been removed from his minor league rehab assignment. The lefty reliever was completing a rehab at Triple-A Syracuse from lat surgery and was days away from potentially rejoining the club.  “We’re not too concerned, but we’ll probably give him a couple or few days and then he will continue to throw,” Mendoza said before the Mets’ 10-5 win over the Rockies on Wednesday .  Minter was scheduled to pitch back-to-back games for the first time in his rehab beginning Wednesday, the last hurdle before rejoining the Mets.  “He’s not too concerned, but the fact he reported it we’re doing that,” Mendoza said.  New York Mets pitcher A.J. Minter hit a setback in his rehab.…