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
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.
The start and finish locations of the first ever Tour de Yorkshire international cycle race have been announced today - with the East Riding set to play a major part after missing out in the Grand Depart in the summer. Bridlington will host part of the race, along with Scarborough, Leeds, Selby, Wakefield and York. We don't know the exact route yet but details will be revealed next month. It's hoped the region can capitalise on the success of last summer's Tour de France opening stages which saw more than three million people cheer on the cyclists as they rode through Yorkshire. Michael Billington reports.
Leeds defender Giuseppe Bellusci has been charged with misconduct for allegedly using racist language towards Norwich striker Cameron Jerome during the Championship match on October 21 the Football Association has announced. Bellusci has until January 2 to respond.
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.
The start and finish locations of the first ever Tour de Yorkshire international cycle race have been announced. Bridlington, Leeds, Scarborough, Selby, Wakefield and York were unveiled as the start and finish lines of the three day race by organisers Welcome to Yorkshire this morning. The race will be held betwen the first and the third of May, but the exact route will be revealed next month.
The six start/finishes for the 2015 Tour de Yorkshire are Bridlington, Leeds, Scarborough, Selby, Wakefield and York.Read the full story ›
The start and finish lines have been announced for the first Tour de Yorkshire international cycle race.Read the full story ›