The Professional Footballers' Association have visited Carlisle in hospital.
In a short statement it said: "Everyone at the PFA is keeping Clarke Carlisle in their prayers and thoughts.
"We visited Clarke at the hospital yesterday and we are offering our full help and support to him and his family at this difficult time."
Footballers who know Clarke Carlisle as a colleague and former chair of their players' association have tweeted their shock at the news of his involvement in a collision with a lorry.
Just heard the news about Clarke Carlisle. My thoughts are with his friends and family.
Shocked to hear the news tonight about Clarkey, thoughts with him and his family. Pull through mate
Clarke Carlisle's wife, Gemma, has tweeted her thanks to those who have sent her messages of support after her former York City footballer husband was hit by a lorry.
Don't normally use this account anymore. But have been overwhelmed with your thoughts and prayers. Thank you
The world of football pledged its support and best wishes to former Professional Footballers' Association chairman Clarke Carlisle following reports he had been seriously injured in a collision with a lorry on Monday.
North Yorkshire Police said a 35-year-old man was airlifted to hospital after a serious incident involving a lorry and a pedestrian on the A64, near York, on Monday morning.
The force would not confirm the injured man's identity, but last night social media was full of messages from well-wishers hoping Carlisle, 35, makes a quick recovery.
The Football Association tweeted: "The thoughts & prayers of all at The FA are with Clarke Carlisle & his family at this sad time."
Anti-racism organisation Kick It Out, for which Carlisle is an ambassador, posted: "The thoughts and prayers of everyone at Kick It Out are with Clarke Carlisle and his family. Stay strong our dear friend - keep on fighting."
And the Football League added: "Our thoughts & those of everyone that watches Football League clubs will be with Clarke Carlisle and his family this evening."
Police have appealed for witnesses to the collision on the A64 near the village of Bishopthorpe, at 7.30am on Monday.
"The collision involved a male pedestrian and a lorry.
"The injured man has been airlifted to Leeds General Infirmary with serious injuries.
"The road was closed to allow the air ambulance to land and to allow collision investigators to examine the scene."
Carlisle played as a centre-half for a number of clubs including Burnley, Blackpool, QPR, Leeds, Watford, Northampton and York.
After he stopped playing, he worked for the PFA and was also a regular on TV - both as a pundit but also as a contestant on the long-running Channel 4 quiz show Countdown and a guest on the BBC's Question Time.
He has also presented a TV documentary about racism in the game and another Football's Suicide Secret - about mental health issues among his fellow professionals.
It is understood that former Leeds United and York City player Clarke Carlisle is being treated at Leeds General Infirmary after being hit by a lorry.
Police are appealing for witnesses to a serious collision on the A64 near Bishopthorpe in York at 7.30am on Monday.
North Yorkshire Police would only confirm that an injured man was airlifted to hospital with serious injuries.
The thoughts & prayers of all at The FA are with Clarke Carlisle & his family at this sad time.
Our thoughts are with former defender Clarke Carlisle and his family following tonight's sad news.
York City Football Club and the City of York Council have approved an agreement which will see the club take a long term tenancy at their new home. The agreement also secures £2million funding contribution towards the new stadium.
The 8000 all-seater stadium and leisure complex will be the first of its kind for York. It will also have fitness and play areas, as well as a community hub focussed on providing health services for residents.
With no games in the Premier League and the Championship because of the international break, teams in Leagues One and Two can claim their share of the limelight.
York City, face an important seven days with a cup replay, and two matches against sides down with them at the wrong end of the table. First up on Saturday Oxford United visit Bootham Crescent.
Since Russ Wilcox took over from Nigel Worthington a month ago, the Minstermen have only lost one of their five matches and they are unbeaten in their last four:
York Police are urging the public to report sightings of a man who failed to turn up for court.
John Alcock, aged 46, failed to appear at court to answer a charge of common assault.
Alcock, is also wanted for breaching his bail conditions.
Officers have been carrying out checks at various address throughout York in effort to locate Alcock, who is believed to still be in the city.
Police are urging people to help them find Alcock by reporting sightings of anyone matching his description.
He is described as white, around 5ft 6in tall, with a medium build, brown hair and brown eyes.
Anyone with information should contact police and quote reference number 12140181715.
Both Mark Robins and Russ Wilcox take charge of their new teams for the first time tomorrow afternoon.
Robins, who was appointed Scunthorpe's new manager on Monday, will be hoping for a good start when the Iron welcome Colchester.
Scunthorpe's former boss Russ Wilcox kicks off his York City reign with the visit of Shrewsbury
Russ Wilcox has been appointed the new manager at York City. Wilcox, who was only sacked by Scunthorpe last week, takes over from Nigel Worthington who resigned on Monday. His first job is to lift the Minstermen from 22nd in league 2. Phil Roscoe reports.