Burnley defender Michael Keane had "no memory" of the preceding week after suffering concussion in the club's 2-0 win over Rotherham last month, and has revealed he forgot what year it was after suffering a blow to the head during the game.
Keane, 23, initially played on after a clash of heads early in the game, but was substituted on 32 minutes and has now revealed the extent of his symptoms.
"I felt alright to go on, but I went down from a set play and said to the physio I couldn't see," the centre-back told BBC Radio Lancashire. "At first I was just really dizzy all the time and had no memory of the past week, really.
"The doctor asked me what year it was and I thought it was 1996. I was all over the place.
"I got treated really well at the hospital, had a few scans and then had to take my time to get back to normal and thankfully now I am alright.
"Looking back, [substituting me] was definitely the right thing to do.
"They have to be extra cautious when it comes to head injuries and rightly so because you can get massive injuries to your brain."
If in doubt, sit them out: read FA concussion guidelines ahead of this weekend's football https://t.co/CQxyLV31eP pic.twitter.com/9mzjXS3XBj
- The FA (@FA) December 18, 2015
Earlier this season the Football Association released updated guidelines for concussion protocol, stating that "anyone with a suspected concussion must be immediately removed from play."
Concussion has been a major talking point in the sport for a number of seasons, with Germany midfielder Christoph Kramer's substitution in the World Cup final the most high-profile incident.