The Premier League is a physically and mentally draining division. It takes its toll on all players, and squads that are too small or fragile can be chewed up and spat out.
Although a strong and consistent core of players in the starting lineup is essential, substitutes who can make a difference with their fresh legs or easily slot into the team for the occasional match are just as important.
When injuries come into play, substitutes can play a massive role in the course of a season. Divock Origi played the hero in Liverpool's Champions League campaign and earned himself a long-term contract as a result.