Luton captain Tom Lockyer was taken to hospital after collapsing early in the first half against Coventry at Wembley.
The 28-year-old was running backwards towards his own goal when he fell to the ground and was unable to get back up.
Medical staff were immediately in attendance and Lockyer was conscious as he left the field on a stretcher wearing an oxygen mask.
The Wales international was taken to the stadium's medical room, where his parents joined him, before going to a specialist hospital in North London for further tests.
Luton tweeted: 'We are able to report that after collapsing on the pitch, Tom Lockyer has been taken to hospital for further tests.