Football is a squad game, they keep telling us. It's not about 11 players on the pitch, it's about a group of 18, 20, 25 that contribute over the course of a season.
It's no use, then, having a top group of starters if those that come in to replace as managers shuffle their packs aren't up to standard.
People don't think about goalkeepers in that way, but it matters just as much. You have a starter, but what happens if they get injured, or suspended, or go through a bad patch?
Depth between the sticks is just as vitally important as any other position on the pitch. But which Premier League clubs have the greatest depth in goal?
This is not about having a top number one, but a completely dependable back-up as well.
8. Ben Foster/Boaz Myhill - West Bromwich Albion
Ben Foster is one of the best shot stoppers in the Premier League and at 34 years of age is as experienced as they come after 11 straight seasons of top flight football with Watford, Manchester United, Birmingham and now West Brom.
Beneath him at the Hawthorns, Boaz Myhill is an equally good shot stopper. The former Wales international hasn't played league football this season because of Foster, but the Baggies would feel equally assured with whichever donning the gloves.
7. Claudio Bravo/Willy Caballero - Manchester City
It wasn't long ago that Claudio Bravo was considered among the top goalkeepers in the world and, despite a very difficult year with Manchester City, he hasn't automatically become a bad one. Even if he's not grouped with the Premier League elite.
In Willy Caballero, City have a safe pair of hands in reserve, hands that Pep Guardiola has called upon numerous times this season.
6. Kasper Schmeichel/Rob-Robert Zieler - Leicester City
Established number one Kasper Schmeichel was joined at Leicester last summer by German international Ron-Robert Zieler, a player schooled for five years by Manchester United in his younger days.
Schmeichel is already known as one of the best in the Premier League, but Zieler was a Bundesliga ever-present for five years before returning to England and was part of Germany's World Cup winning squad in 2014.
5. Jack Butland/Lee Grant - Stoke City
Widely considered one of the best goalkeepers in the Premier League, Jack Butland recently returned to action for Stoke after a full year sidelined with injury.
Prior to his recovery, Lee Grant has served all season as a more than capable deputy, giving Stoke now a surprising level of depth between the sticks. Grant, who signed permanently from Derby in January, had never even played top flight football before this season.
4. Petr Cech/David Ospina - Arsenal
Petr Cech is not quite as good as he used to be, and David Ospina is not the same keeper that starred for Colombia at the 2014 World Cup, but both are still solid options and the majority of Premier League clubs would kill to have one or the other, let alone both.
The fact that Wojciech Szczesny may yet return from two years on loan at Roma only stands to make the Gunners stronger. There won't be room for all three next season, though.
3. Hugo Lloris/Michel Vorm - Tottenham Hotspur
Dutch international Michel Vorm was a top Premier League starting goalkeeper before he moved to Tottenham in 2014 to become Huge Lloris' understudy.
Lloris, who is also Spurs captain, is rightly rated incredibly highly and Vorm adds a degree of depth to the position that most other clubs just don't have.
2. David de Gea/Sergio Romero - Manchester United
Nearly two years after he joined the club for free as a former favourite of Louis van Gaal, Manchester United fans have finally warmed to Sergio Romero this season.
The Argentina number one has largely been first choice on the club's run to the Europa League final and has never yet let the side down whenever he's been given the nod. To then have world class David de Gea in front is plain ridiculous.
1. Thibaut Courtois/Asmir Begovic - Chelsea
Thibaut Courtois is arguably the Premier League's only other 'world class' goalkeeper besides De Gea and Chelsea have a long established Premier League deputy who is more than capable of being a number one at most other clubs, Asmir Begovic.
The Bosnian international nearly left Stamford Bridge in January in pursuit of first-team action and the issue is sure to resurface again this summer. For now, though, there is no better pair of Premier League goalkeepers than at Chelsea.