Substitutions are a key part of football, managers able to turn to a bench of seven and introduce three of them.
However, it was not until August 1965 that substitutes became a feature of the English league game.
Teams were able to name one sub then, that number increased to two in 1987 and gradually up to the seven we have now.
Preston North End used a sub in a league game for the first time on September 1, 1965.
Frank Lee replaced Dave Wilson nine minutes from the end of their 4-1 defeat against Portsmouth at Fratton Park.
In the 1965/66 season, PNE used 11 substitutes in their 42 Second Division matches.
A history of North End substitutes has been compiled by PNE fan and statistician Tony Woodburn.
For a number of years, Woodburn was the National Football Museum’s joint PNE historical statistician.
Woodburn, who attended his first North End game in 1967, has produced a booklet titled ‘PNE Substitute’.
He has listed a number of stats about the substitutions made by Preston down the years which makes for some interesting reading.
Archie Gemmill was the first player to make his PNE debut as a substitute.
Gemmill also scored after coming on in a 3-1 victory at Norwich in August 1967.
Only three other debutantes have done what Gemmill did, David Beckham, Richard Cresswell and Paul Reid.
Joe Garner is the only PNE sub to have scored a hat-trick, that coming in an FA Cup replay against Ipswich in January 2014.
The highest-scoring North End substitute is Patrick Agyemang with eight goals.
Cresswell and Jason Harris could be classed as ‘super subs’ having both scored five times from the bench in a single campaign.
The most subbed Preston player in history was Chris Sedgwick, the winger taken off 100 times – very often we witnessed the ‘Sedgwick walk’ when Billly Davies was boss.
Jon Macken is second in that list having been taken off in 86 games.
The first goalkeeper to come off the bench for PNE was Lee Bamber at Mansfield in 1993 –Bamber was needed after Kelham O’Hanlon was sent-off.
The 'PNE Substitute' booklet costs £6 including postage and is available from www.pnesub.co.uk.