You only need one keeper in your squad.
In my 35 seasons I've played 989 games. My top appearances was a keeper with 544 games and my present keeper has played 407 times.
So two keepers have accounted for 951 out of 989 games.
I think I had another academy player who filled in for a couple of seasons.
I gave up judging them on form a long time ago as quite often you see the highest ratings come when the team is losing/tanking as that is when the keeper is busiest.