Lee Roberts, aged 52, is in hospital with serious injuries after a Mercedes ploughed into him outside the racecourse on York Road on Saturday.
The crash claimed the life of Lee's friend, 65-year-old Adrian Scott, who died at the scene.
The two men were associated with the Birstall Victoria rugby league club, where Lee coached the open-age team and Adrian was a former physio.
Lee is self-employed and a GoFundMe page has been set up to support him financially, with a first target of £5,000.
Nigel Harnell, who launched the fundraiser on Sunday, said: "Waking up to the terrible news this morning that Lee and his friend Aidy had been in a terrible accident.
"Devastated to learn his friend has lost his life and Lee has what it sounds like has sustained life changing injuries and is critical in LGI.
"As a close friend of Lees and as work colleagues, I know it will financially hit him hard as he is self employed.
"I know this is the least of Lee's worries at the moment but lets at least take one worry off his mind in what is a terrible and heartbreaking tragedy."
The driver of the Mercedes involved in the crash was arrested on suspicion of dangerous driving and later released under investigation.
Tributes paid to Adrian Scott
Family and friends have paid tribute to 'well-loved' grandad Adrian Scott, as they thanked emergency services for their help at the scene.
Wetherby Racecourse has also released a statement this morning.
A spokesperson said: "Everyone at Wetherby Racecourse is deeply saddened to learn that the gentlemen that were involved in the tragic accident on Saturday evening had been racing with us during the day and our thoughts and heartfelt sympathies go to the families of both Mr Scott and Mr Roberts at this time."