A cigarette butt left smouldering on a sofa caused damage estimated at £200,000 to the social club at Witney's Marriotts Stadium.
But the chairman of Witney Academy football club, Brian Constable, said the club's first home game of the season would go ahead as planned on Wednesday.
The fire was confined to the downstairs night club at the former home of Witney Town Football Club. The changing rooms and seating in the stadium were unaffected.
But new wiring, flooring and ceiling tiles will make the repair bill costly. Lighting and DJ equipment were also destroyed.
Mr Constable said: "The cause has been given by the fire brigade as a cigarette in the back of a two-seat settee. We are looking at £200,000 damage caused by a cigarette butt."
Initially it was feared that the blaze may have been started by arsonists. The chairman and other people connected with Witney Town have received death threats since the decision to close the club.
Mr Constable then took over as chairman of Witney Academy which plays in the Cherry Red Records Hellenic League Division One West. He felt a fire on the first day of the season may have been more than a coincidence.
Police had been called following a break-in in which kit was stolen six weeks ago, but had not been told of the abuse, which Mr Constable had chosen to ignore.
But an investigation on Saturday revealed the cause had been a smouldering cigarette. A sniffer dog failed to find any signs of arson.
The alarm was raised at 6.45am on Saturday by a member of the public who saw smoke coming from the building, in Downs Road.
Thirty firefighters brought the blaze under control in an hour.
Witney Academy's first game of the season, away against Ardley United, went ahead as planned.
A joint 21st birthday party scheduled for Saturday night was cancelled.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article