Zlatan Ibrahimovic has been a hit, Matteo Darmian a miss while the jury is still out on Henrikh Mkhitaryan... how good is Manchester United's strength in depth after their League Cup exit?

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The biggest shock of the League Cup came on Wednesday night when holders Manchester United were dumped out of the quarter-finals at Bristol City 2-1.

After the match manager Jose Mourinho was critical of his side's display at Ashton Gate, stating: 'It's a big day for them [Bristol City] and their supporters. 

'For us it was just one more day in the office and some of them probably didn't want to come into the office. 

Korey Smith (right) was Bristol City's matchwinner as they beat Manchester United 2-1

United boss Jose Mourinho was critical of his side's approach going into the League Cup tie

'They fought like this was the game of their lives which it probably was. It was a beautiful day for football.

'I congratulate them. The main thing of it is that they won. [We] lacked the intensity that they had. Not just physically but mentally.'

Having fielded a weakened side for the tie, despite the likes of Paul Pogba and Zlatan Ibrahimovic starting, questions will be asked about United's strength in depth.

Here, Sportsmail takes a look at the back-up options available to Mourinho and whether or not they're good enough.

NB: United's probable best starting XI (when everyone's fit):  De Gea; Valencia, Bailly, Jones, Young; Pogba, Matic, Herrera; Martial, Lukaku, Rashford.

Mourinho reacts on the touchline at Ashton Gate as his weakened side lose their quarter-final

GOALKEEEPERS

Sergio Romero

Has been a more than reliable No 2, since joining the club in 2015, and is arguably the best back-up goalkeeper in the Premier League. Started in goal for last season's Europa League success too.

Verdict: HIT

Sergio Romero has been a dependable No 2 for United since joining the club in 2015

Joel Pereira

The 21-year-old is third-choice but clearly Mourinho has faith in the youngster, bringing him on as a substitute three times so far in his fledgling career.

Verdict: JURY OUT

Joel Pereira has made three substitute appearances in his United career under Mourinho

DEFENDERS

Daley Blind

The utility man has played at left back, centre back, left-wing back and central midfield during his time at Old Trafford so far - providing Mourinho with many options when short. Makes up for his lack of pace with intelligence as depicted with a brilliant tackle on Bristol City striker Korey Smith during the first half.

Verdict: HIT

Daley Blind (centre) braces himself for a goal-saving tackle on Smith during the first half

Matteo Darmian

Adept at playing right or left back, Darmian's attacking qualities as a full back don't compare to those in front of him in the pecking order - thus often hindering attacks.

Verdict: MISS

Matteo Darmian's (left) attacking game doesn't compare to his fellow team-mates at full back

Victor Lindelof

Bought in the summer for £31million, the Swedish centre back hasn't lived up to his billing so far. His display in the 2-1 defeat at Huddersfield encapsulates that - however, United fans will remember that Nemanja Vidic and Patrice Evra didn't have the best starts to their careers there too...

Verdict: JURY OUT

Victor Lindelof hasn't lived up to his £31million price tag since moving from Benfica

Marcos Rojo

The rugged Argentine more than proved himself last season before he was curtailed by a knee injury in April. Now back fit, he will be looking to force his way back into the starting XI despite Wednesday night's loss. Definitely more comfortable at centre back than at left back.

Verdict: HIT

Marcos Rojo (right) will be looking to win back his place in the starting XI after a knee injury

Luke Shaw

Probably the biggest enigma within the Red Devils squad. Has the natural talent to be the No 1 left back for club and country for the next decade but his form over the past year has been erratic to say the least. Injuries have played their part but Mourinho clearly has his doubts.

Verdict: MISS

Luke Shaw's (right) time at United could come to an end with Mourinho having his doubts

Chris Smalling

With every centre back fit he's likely facing a battle to partner Eric Bailly in defence, but Smalling is more than adequate cover. The England international may look awkward in possession but he has the physicality to deal with opposition strikers.

Verdict: HIT

Chris Smalling (right) is one option who could partner first-choice centre back Eric Bailly

Axel Tuanzebe

A player of huge promise, the 20-year-old is tipped for a bright future at the Theatre of Dreams.

Verdict: JURY OUT

At 20-years-old, Axel Tuanzebe (right) is tipped for a bright future at Old Trafford

MIDFIELDERS

Michael Carrick

Limited to just one appearance this season, due to injuries, the calming influence in midfield has been sorely missed at times. However, at 36 this could be the club captain's last campaign at Old Trafford.

Verdict: HIT

Michael Carrick's (right) sole outing for United this season came in their 4-1 win over Burton

Marouane Fellaini

Synonymous with the ill-fated David Moyes reign, Fellaini has had a roller-coaster career at Old Trafford. He was booed by supporters last season, after giving a penalty away at Everton, but battled back to win them over with some tenacious displays in midfield. An excellent Plan-B option, he could leave on a free transfer next summer.

Verdict: HIT

Marouane Fellaini could be leaving Manchester United on a free transfer next summer

Jesse Lingard

A homegrown product, he is finally starting to excel for United playing just off striker Romelu Lukaku - with four goals in his last five games highlighting that. Always full of running and endeavour too, he's capable of scoring important goals as the club's most recent FA Cup and League Cup successes point to.

Verdict: HIT

Jesse Lingard (left) has scored four goals in his last five appearances for the Red Devils

Juan Mata

The midfield maestro is a fan favourite and can play anywhere in the attacking positions behind the striker. Being given a chance in the starting XI at present and is taking that with both hands, providing the assist for Lukaku's winner against Bournemouth earlier this month.

Verdict: HIT

Juan Mata (left) is back in the United starting XI and looking to cement his place there

Henrikh Mkhitaryan

The Armenian's United career has been up-and-down so far - being frozen out at times while excelling during others. Scored 10 goals last season, including one in the Europa League final, but is very much not at the forefront of Mourinho's thoughts at present. His substitute appearance at Bristol City was his first since United's 1-0 league win over Brighton on November 25.

Verdict: JURY OUT

Henrikh Mkhitaryan (right) played his first game for United in nearly a month on Wednesday

Scott McTominay

Eight appearances for United this season, including four this month, clearly point to a player that Mourinho trusts. The 21-year-old is still learning his trade but is a powerful midfielder that likes to go from box-to-box.

Verdict: JURY OUT

Scott McTominay has made eight appearances so far this season - including four in Decemeber

STRIKERS

Zlatan Ibrahimovic

Grabbed his first goal of the season on Wednesday night after his brilliant campaign last year, which yielded 28 goals and nine assists in 46 appearances, ended prematurely due to injury.

Verdict: HIT

Zlatan Ibrahimovic scored his first goal of the season on Wednesday - after his knee injury