Leeds' teenage winger Jack Clarke was taken to hospital after complaining of feeling unwell during Saturday's Championship draw at Middlesbrough.
Referee Darren England was forced to suspend the game temporarily as Clarke received treatment on the Leeds bench before being taken to the dressing room for further inspection.
Clarke was taken to hospital and then spent Saturday night in the care of Leeds' medical staff.
"Jack has had messages from football fans from every club you can imagine and we all really appreciate it", Kinnear told the club's official website.
The incident caused a 12 minute delay to the game.
Clarke has impressed in spells for Leeds this season, with the 18-year-old the latest player to come through the ranks at the club.
'Jack has left the hospital now and is happy and smiling.
The game resumed after a break in play, with a dramatic finale seeing Kalvin Phillips level in the 11th minute of stoppage time to earn Leeds a point - and cancel out Lewis Wing's opener.
Clarke's agent, the former Leeds defender Ian Harte, said: 'We'd like to thank Middlesbrough's medical team, and also everyone involved at James Cook Hospital, where the staff have been brilliant.
The result puts Marcelo Bielsa's side back on top of the Championship, one point ahead of Norwich City, who face Ipswich Town on Sunday.