Shaun Whiter went to help Joey Abbs with a flat tyre in Newmarket on Friday night. Both men were pinned against their cars when the vehicle hit them.
Mr Whiter, 27, who was due to begin training with Newmarket Town FC, has lost both legs below the knee.
Mr Abbs, who plays for Soham, sustained a "serious" leg injury.
The Newmarket player, who works as an estate agent in Stansted, is due to marry his fiancee Charlotte Way next July and has vowed to "walk down the aisle".
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The crash happened on Dullingham Road, in the Suffolk town at 22:55 BST.
Mr Abbs' Vauxhall Astra had a flat tyre and, as reported in the Cambridge News, he pulled up on a pavement and called his friend for help.
Mr Whiter came to his aid, parking his black BMW 320 behind.
A Ford Focus then crashed into Mr Whiter, who was standing behind his vehicle.
The force shunted the BMW forward, pinning Mr Abbs between the two cars.
The Ford Focus driver did not stop at the scene, Cambridgeshire Police said.
The force described Mr Abbs' injuries as "serious".
The secretary of Newmarket Town FC confirmed both of Mr Whiter's legs had been amputated.
"He was due to begin pre-season training this evening. We are in shock, absolutely devastated," he told the BBC.
Both Newmarket FC and Cambridgeshire club Soham Town Rangers have tweeted their support for the players, describing them as "great guys".
A Crowdfunding page set up by a friend to help both men has raised almost £6,000.
Ms Way has also set up a fundraising page to help pay for "equipment and aftercare" for her fiancé.
Writing on his Facebook page on Monday night, Mr Whiter said: "It's an amazing feeling knowing each and every one of you are there for support and thank you so much.
"We are 100% fighting to get out of this place and will be with you shortly, but again please keep the visiting up, we love it ‪#‎warriors."
A footballer who went to help a friend in a broken-down car has had both his legs amputated after a hit-and-run driver crashed into their vehicles.