May was suspended for the preliminary final after a charge was leveled against him by the NRL's match review committee, but would have missed the game regardless after suffering a hamstring injury during the club's qualifying final victory over the Parramatta Eels during Week 1 of the finals.
"May has not ben able to overcome a hamstring injury in time for Sunday’s decider at Accor Stadium," a short statement released by the club reads.
The winger, who was this morning selected in Samoa's squad for the Rugby League World Cup, was replaced by Charlie Staines last weekend for the win over the South Sydney Rabbitohs which booked their spot in a third straight grand final.
The Panthers were non-commital over who would replace May this weekend against Parramatta though.
"Panthers coach Ivan Cleary will name the winger’s replacement when official Grand Final teams are announced at 4:00pm on Tuesday," the statement concluded.
The Panthers confirmed at 4pm when teams were named that Charlie Staines would remain in the team for the grand final, despite the Panther having been linked with a move away from the club during the season.
May being ruled out comes as a blow to the Panthers, although his participation in the finals series was controversial from the beginning after he was granted the right to serve a two-game suspension for an off-field incident at the start of next year, rather than during the finals series.
Sunday's grand final will kick-off at 7:30pm (AEST).