Every once in a while, a club may find a player who becomes invaluable to the team.
For Barcelona, that player is Lionel Messi. For Real Madrid, Cristiano Ronaldo.
For over a decade, Liverpool's main man was Steven Gerrard. Clubs will do whatever they can to hold on to players like these three.
Often their team's captains, they're leaders off the pitch and often, the best player on it. And Liverpool aren't the only English club to have one of these legends.
Until last summer, there was no player more valuable at Chelsea than John Terry. Even when he was past his prime, he was still important in the dressing room.
It usually takes years to replace a player of that caliber, so when a manager comes into a new team, they always hope to have one.
Luckily for Manchester United boss Jose Mourinho, he claims to have more than one of those players.
The ex-Chelsea boss has apparently placed a number of names into an elite 'untransferable' bracket at Old Trafford.
The likes of David de Gea and Marcus Rashford are on the list, along with one player who Mourinho believes can replicate Terry at United.
According to the Manchester Evening News, Phil Jones is the man that the Red Devils boss thinks can become as legendary as Aston Villa's new captain.
It's a huge claim from Mourinho, but he must have made a similar one shortly after taking over at Stamford Bridge in 2004.
He turned Terry into one of the best defenders of his generation and the captain led Chelsea to five Premier League titles, FA and League Cups, and Champions League glory.
Jones has already won the league, FA Cup and Europa League at United, so there's nothing stopping him from living up to Mourinho's claims.