Television pundit and former footballer Clarke Carlisle, 35, is in hospital with serious injuries after being involved in a collision with a lorry.
The cause of the accident on the A64 near York is not yet known.
Carlisle, a former Professional Footballers' Association chairman, was airlifted to Leeds General Infirmary.
A PFA statement read: "Everyone is keeping Clarke in their prayers and thoughts. We are offering our full help and support to him and his family."
Clarke's injuries are not life-threatening, the BBC understands,
The PFA's sentiments were echoed by a number of Carlisle's former clubs, among them Burnley and QPR, as well as the Football Association and Football League.
QPR midfielder Joey Barton and former Downing Street communications chief Alastair Campbell, a Burnley fan, took to Twitter to wish Carlisle well.
"Just heard the news about Clarke Carlisle. My thoughts are with his friends and family," Barton wrote.
Campbell tweeted: "Really hoping @clarkecarlisle going be ok. Thoughts with Gemma/two lovely kids. A great @BurnleyOfficial man and mental health campaigner."
Carlisle's wife, Gemma, also used the social networking site to express gratitude to well-wishers.
"Don't normally use this account anymore," she wrote. "But have been overwhelmed with your thoughts and prayers. Thank you."
Equality campaign body Kick It Out, for which Carlisle is an ambassador, tweeted: "Stay strong our dear friend - keep on fighting."
Police have appealed for witnesses to the accident, which happened on the A64 near the village of Bishopthorpe at 07:30 GMT on Monday.
A police spokeswoman said the collision involved a male pedestrian and a lorry, adding that the injured man had been airlifted to Leeds General Infirmary with "serious injuries".
Centre-back Carlisle made more than 500 appearances during a playing career spanning 16 years at nine clubs - Blackpool, QPR, Leeds United, Watford, Luton (loan), Burnley, Preston (loan), York and Northampton.
Married with three children, he retired in 2013 after Northampton were beaten by Bradford in the League Two play-off final.
Carlisle succeeded Chris Powell as PFA chairman in November 2010 and relinquished the role last year.