They were discovered at Hamlin Lane playing fields in Exeter on Friday morning, the day before various teams were set to kick off the season.
The six-pitch council-owned complex is managed by Stoke Hill AFC, but is used by nine other clubs who field a full range of junior and adult squads.
Exeter City Council said it is applying for an eviction order.
Police are also investigating claims locks were broken at the site, where a group of about 15 caravans were parked.
Stoke Hill chairman, Paul Howe, said he was sympathetic with the travellers' need for space, but up to 200 players had been disappointed.
He said: "I was recommended by the police not to hold any football matches, which was the start of the season for our youth teams and a number of adult teams, so everything had to be cancelled.
"They felt it was in our best interest to not antagonise them (the travellers) in any way."
Mr Howe said he was trying to secure alternative venues for next weekend.
"It's a problem every summer," he said.
"I do have some sympathy but at the same time they have disrupted what was the start of the season for a number of boys who were looking forward to playing football."
Exeter City Council leader Pete Edwards said: "We are moving as quickly as we can but there are certain hurdles that need to be cleared before we can gain a possession order from the courts."
Hundreds of footballers missed the start of their season after a group of travellers set up camp on their pitch.