Burnley defender Michael Keane has revealed he believed it was 1996 and had "no memory" of the previous week after suffering from concussion.
Keane, 23, initially continued playing after a clash of heads during the 2-0 win over Rotherham on 20 February.
But he was substituted on 32 minutes and missed the next two matches, returning on 5 March against Blackburn.
"I felt alright to go on but I went down from a set play and said to the physio I couldn't see," Keane said.
In November 2015, the Football Association released new guidelines that stated "anyone with a suspected concussion must be immediately removed from play".
Keane added that it took him a while to get back to feeling "normal" following his injury.
"At first I was just really dizzy all the time and had no memory of the past week, really," he told BBC Radio Lancashire.
"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."