Former clubs and team-mates of Jackie McNamara have sent their best wishes after the former Scotland international fell seriously ill.
The 46-year-old is understood to have been admitted to hospital for brain surgery.
McNamara's family wrote on Twitter that he was receiving the "best care possible".
Reports say he is being treated in Hull, having first been taken to hospital in York after collapsing near his home in the city on Saturday.
A post on McNamara's personal Twitter account read: "This is Jackie's daughter. Thank you all for your kind words and support. My dad is getting the best care possible, as you all can understand this is difficult for us as a family and request privacy at this time."
Hartson wrote on Twitter: "Worried sick for my former teammate and great friend Jackie McNamara who collapsed at home Saturday with a bleed on the brain.. my thoughts are with his wife Samantha and the children."
The Scottish champions wrote on Twitter: "The thoughts and prayers of everyone at #CelticFC are with Jackie and his family."
Former Celtic striker Chris Sutton added: "Thoughts and prayers for Jackie and Sam and the family."
A statement on the Scotland National Team Twitter account read: "The thoughts of everyone at the Scottish FA are with former Scotland player Jackie McNamara and his family."
Other former clubs including Aberdeen, Wolves and Dundee United also sent their best wishes.
The former Dundee United, Partick Thistle and York manager has been working as a players' agent as well as advising Dunfermline through his sports management firm.
McNamara recently opened a sports bar in Fuengirola, Spain, with Simon Donnelly, his former Celtic team-mate and managerial assistant and close friend.
His father, Jackie McNamara Snr, played for Hibernian and Celtic.