2:15 Watch some of the best and worst moments from Man City and Liverpool goalkeepers this season Watch some of the best and worst moments from Man City and Liverpool goalkeepers this season

Ahead of Manchester City v Liverpool live on Sky Sports this Sunday, we compare the clubs' four 'keepers that have fallen in and out of favour.

Manchester City and Liverpool started the season in scintillating form but both clubs suffered dips that coincided with goalkeeper troubles.

City boss Pep Guardiola axed Joe Hart and signed Claudio Bravo for £17.1m from Barcelona in the summer due to the Chilean's superior footwork.

But Bravo made a costly error on his debut against Manchester United, failing to claim a cross and colliding with team-mate John Stones before Zlatan Ibrahimovic applied the finish to score a consolation goal.

As the weeks went by, Bravo faced growing criticism about his shot-stopping abilities, with the situation coming to a head after back-to-back defeats to Chelsea and Leicester in December.

Manchester City's Willy Caballero (left) has replaced Claudio Bravo in goal

Pep Guardiola made the decision to replace Bravo with reserve stopper Willy Cabellero when a shock 4-0 defeat to Everton was followed by a 2-2 draw with Tottenham in January.

Meanwhile, Liverpool boss Jurgen Klopp signed Loris Karius from Mainz for £4.7m in the summer to replace Simon Mignolet - but the 23-year-old German also faced growing criticism for his shot-stopping last year.

Liverpool's Simon Mignolet has replaced Loris Karius in goal

Mignolet was reinstated as the Reds' No 1 after Karius made a costly error during a 4-3 defeat to Bournemouth and another in the following 2-2 draw with West Ham in December.

But were the respective managers correct to drop their No 1 stoppers, and where do the four rank among other Premier League 'keepers this term?

WHAT THE STATS SAY…

Pep Guardiola was right to drop Bravo, while Klopp was wrong, marginally, to reinstate Mignolet, according to Opta's expected goals (xG) model.

The model factors shots on target and the likelihood of those shots finding the back of the net, based on the angle, distance and placement of each shot. The original quality of the chance before the player shoots is also considered.

Out of the four 'keepers in question, the model suggests Caballero has outperformed the rest, saving 16 per cent of shots that would be expected to hit the back of the net this season.

Man City and Liverpool 'keeper stats total Player Saves Errors leading to goals Clean sheets Goals conceded Mins played Bravo 31 1 4 25 1,710 Mignolet 34 1 4 23 1,620 Caballero 13 0 4 4 720 Karius 20 2 3 12 900

But he's the only stopper out of the four to record positive figures. Karius has conceded 14 per cent of shots that should have been saved, while Mignolet has leaked 16 per cent of strikes that should have been stopped.

But Bravo dwarfs those figures. The Chilean has conceded 27 per cent of shots that should have been saved, according to Opta's model.

MAN CITY

Caballero's impressive results in Opta's expected goals model are backed up with more stats.

He has only conceded a goal every 180 minutes - that's the best rate of any Premier League goalkeeper that has played more than 700 minutes this season.

The Argentine ranks as the league's fifth most effective shot-stopper, in terms of his ratio of expected goals prevented, and he is one of 10 keepers that have not made a single error leading to a goal.

In addition, the 35-year-old ranks second in the Premier League for overall save percentage and second for save percentage from shots in the box.

DID YOU KNOW? On average, one shot out of three on target is scored.

In contrast, Bravo ranks 25th out of 28 for shot-stopping, third-bottom for overall save percentage, bottom for save percentage from shots inside the box, 16th for costly errors and 14th for minutes-per-goal conceded.

Following City's 3-1 defeat to Chelsea, Bravo conceded more goals than he made saves in six out of nine appearances.

That isn't uncommon in a Premier League match - it's happened on 102 occasions during 551 appearances by 'keepers this season. But in six out of nine matches at a top club? Questionable.

The 33-year-old leaked six goals without making a single save during his last two games before being dropped, against Everton and Spurs.

DID YOU KNOW? The average save percentage is 67 per cent, while the average save percentage from shots taken in the box is 57 per cent.

LIVERPOOL

Mignolet ranks 22nd for shot-stopping, 23rd for overall save percentage, 20th for save percentage from shots from inside the box, 11th for minutes-per-goal conceded and has made one error leading to a goal.

Karius ranks above Mignolet for shot-stopping in 21st, 20th for overall save percentage, 22nd for saving shots in the box, eighth for minutes-per-goal conceded.

However, the German ranks joint-bottom for costly errors, following his two successive mistakes that led to losing his starting place.

Where do they rank among PL 'keepers this season (700+ mins)? 'Keeper Shot-stopping effectiveness Least error-prone (per 90) Overall save % Save % from shots in the box Mins per goal conceded Bravo 25th 16th 26th 28th 14th Mignolet 22nd 18th 23rd 20th 11th Caballero 5th 1st 2nd 2nd 1st Karius 21st 28th 20th 22nd 8th

Caballero appears to have settled the 'keeper crisis at City, but Liverpool's situation remains less certain. Meanwhile, City's out-of-favour Joe Hart continues to ply his trade 1,000 miles from Manchester in Turin...

Will Caballero be the difference when City host Liverpool? Let us know in the comments section below or tweet us @SkyFootball

Watch Manchester City v Liverpool live on Sky Sports 1 from 4pm on Sunday