The Labour leader said coronavirus has had a huge impact on the likes of Walsall FC and Shrewsbury Town FC and others across the country.
And he said he would welcome the return of football fans to help clubs bounce back – but only if it could be done safely amid the pandemic.
Sir Keir said the clubs mean "something more than just football" and said he didn't want to see teams "go to the wall" as a result of the virus.
The Holborn and St Pancras MP, who toured Walsall FC as part of Liam Byrne's campaign for West Midlands Mayor, said clubs were "huge assets" to the community.
He said: "This pandemic has had a huge impact on clubs like Walsall and Shrewsbury. These clubs are at the heart of their communities.
"For many local people, attending a game at the weekend is something they usually enjoy year in, year out.
"But these clubs are also businesses. What I heard [during the visit to Walsall FC] was that without fans, the future is looking increasingly difficult for clubs outside the Premier League.
"So it was encouraging to see the amount of work that has gone into getting fans back into Bescot safely."
The Labour leader called for struggling clubs to be handed "every bit of help" possible to ensure they can survive the pandemic and keep being at the "centre of communities".
Sir Keir, who was met with cheers and requests for pictures during his visit to Walsall town centre, said the return of football fans would also boost the local economy.
"It’s incredibly important. On match days, fans don’t just go for the game and leave. They go to the pub, pop to the shops and spend time with friends," he said.
"Clubs like Walsall and Shrewsbury are huge assets to the local economy and that is why this pandemic has been so difficult.
"This isn’t just about the local economy, though. I saw first-hand how Walsall went above and beyond to help local people during the pandemic.
"Up and down the country, other clubs are doing the same. They are part of our community.
"I pay tribute to Walsall for its work in the community and, although an Arsenal fan, wish them the best of luck for this season."
Government chiefs have given approval to a handful of teams to stage pilots of fans returning – with numbers currently capped at up to 1,000 allowed due to rising virus cases.
And plans for spectators to attend events in England from October 1 will be reviewed due to the increase in coronavirus cases, Prime Minister Boris Johnson said.