The Rushden & Diamonds player, Ritchie Hanlon, claims he was attacked by a baton-wielding policeman after his side beat Rochdale 2-1 on Tuesday to reach the Third Division play-off final in Cardiff.
Hanlon said he was attacked after pulling a rival fan off a team-mate during a pitch invasion by both sets of supporters after the final whistle.
"One of their fans kicked Butts [Gary Butterworth] and I pulled him off," Hanlon said. "Then a policeman started laying into me. He whacked me with his baton and my knee is really starting to hurt now. I've no chance for Cardiff."
A police spokesman told the paper he was unaware of the incident, but the club is expected to take the matter further. "He was beaten by police and has marks across both legs," the Rushden doctor, Mark Pepperman, said. "There was no reason for it, but the referee assessor saw what happened. I can't believe it."
Rushden will meet Cheltenham at the Millennium Stadium in Cardiff on Monday for a place in the Second Division.
The Cheltenham manager Steve Cotterill allowed his players just one night to savour their penalty shoot-out success over Hartlepool in the other play-off semi-final before it was back to work.
The Robins were victorious when, following a 1-1 draw after extra-time, the Hartlepool forward Ritchie Humphreys missed the decisive spot-kick.
Cotterill said: "They didn't have that long to celebrate, they were in for training at 11am the next morning. That's just the way it is with the final only days away."
Cotterill admits the final will be a highlight of his managerial career. "Leading the team out at Cardiff will be a proud moment for myself," he said. "The young players will be really hungry for it, while the old pros like Tony Naylor – who has played at Wembley before – will be relishing the chance to do it again. Once you've had a taste of it you want to go back for more."
The Hartlepool manager, Chris Turner, was left to reflect on what might have been for a third time, as the club made it an unwanted record of three successive play-off defeats.
He said: "It's disappointing to go out on penalties because someone has to miss in the end. Missing a penalty in that situation stays with you through your career, but that's life."Reuse content