Luton's Premier League clash against Bournemouth was abandoned on Saturday as Hatters captain Tom Lockyer was rushed to hospital after collapsing during the second half.
With the score level at 1-1 in the 65th minute, Lockyer suddenly fell to the turf in a worrying scene.
Play was paused as the Luton defender received treatment from medics while both sides were sent to the dressing room.
Lockyer was eventually stretchered off, surrounded by the medical team, and taken immediately to hospital.
There was a standing ovation from the crowd, with fans in the Vitality Stadium chanting Lockyer's name.
Luton later revealed in a statement that Lockyer was "responsive", but said they were unable to determine exactly what had happened to their player.
Around half an hour after the incident, referee Simon Hooper confirmed the game would not restart on Saturday.
Players from both sides returned to the pitch and applauded the crowd.
"We all hope and pray for our leader and captain Tom Lockyer, who is thankfully responsive and has been taken to hospital," Luton's statement said.
"We don't know the full extent of what happened and what the next steps are at this stage, but we thank Bournemouth and the medical staff on both sides for their immediate response, which was absolutely amazing.
"We are sorry to all supporters present that players from both sides were in no state of mind to continue with the game after seeing their much-loved team-mate and friend taken off like that, and staff could not carry on with managing the game in such circumstances having had to deal with the situation.
"We thank everyone for the wonderful applause and singing of Locks' name inside the stadium at such a difficult time. Now is the time for all of our players, staff and supporters to come together as we always do and give our love and support to Tom and his family.
"Our thoughts are with him and them all."
Lockyer also collapsed during Luton's Championship play-off final win against Coventry at Wembley in May.
The Wales international was taken to hospital and later underwent heart surgery.
The 29-year-old had an operation to correct an atrial fibrillation, a condition the UK's National Health Service (NHS) describes as causing "an irregular and often abnormally fast heart rate".
