The EFL Cup's Round of 16 threw up some fantastic fixtures and they certainly didn't disappoint, the most high-profile being the Manchester Derby.The second instalment we've received already this season, last night's match was an energetic and intriguing affair, even if the two slightly weakened sides lacked the cutting edge we've come to expect from Manchester City and Manchester United.Red Devils midfielder Juan Mata proved to be the difference, capitalising on some chaos in the box to slot the ball past Willy Caballero on the 52nd-minute mark.Goal-mouth excitement was otherwise rather limited - in fact, City finished the match without a single shot on target - and neither side came truly close to hitting top gear.But with youngsters, squad players and one of the most enthralling managerial rivalries in world football thrown into the mix, there was plenty to be learnt from United's 1-0 win over their local rivals.

Mata must start vs Burnley

Jose Mourinho and Juan Mata have formed somewhat of an unholy alliance since the former turned up at Old Trafford in the summer, putting their prior problems at Chelsea aside. It's clear the Portuguese still isn't convinced by the attacking midfielder, leaving him out of the starting XIs to face Liverpool and Chelsea, but Mata is undoubtedly producing when given the chance.

Indeed, he scored the winner yesterday evening but perhaps more importantly from Mourinho's perspective, worked tirelessly until being brought off in the 72nd minute. As much as the solitary goal, a superb slide tackle on City left-back Gael Clichy epitomised his evening.

Having scored United's only goal in their last three games, Mata must start against Burnley at Old Trafford on Saturday.

Garcia can be Guardiola's Golden Boy

aleix-garcia-passing-vs-man-united

When Pep Guardiola took over the Barcelona first-team in 2012, he immediately promoted Pedro and Sergio Busquets from the B squad. The duo quickly became integral members of the Catalans' starting XI as champions of Guardiola's tiki-taka style, going on to win a succession of European and domestic titles together.

It's far too early to suggest similar success for Aleix Garcia, but he could well be the City youngster who suddenly finds himself at the forefront of Guardiola's first team plans. The 19-year-old's performance was solid if lacking real show-stopping impact, but he completed a staggering 90 passes last night, the most of any player on any side, with a completion rate of 94.4%.

He fits the Guardiola philosophy perfectly and and could soon be called upon regularly to help further implement it at the Etihad Stadium.

Marcus Rashford needs time up top

Football Soccer Britain - Manchester United v Manchester City - EFL Cup Fourth Round - Old Trafford - 26/10/16
Manchester United's Marcus Rashford in action with Manchester City's Pablo Maffeo
Action Images via Reuters / Jason Cairnduff
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You can't fault Jose Mourinho for the amount of game time he's issued Marcus Rashford this season - the Portuguese clearly recognises the 18-year-old is a sensational talent for his age and has now handed him three straight starts against some of United's biggest rivals, namely Liverpool, Chelsea and Manchester City.

But if Rashford is going to further improve over the course of the season, it's imperative he's given chances to impress up front. Composure, quality and instinct in front of goal remain the teenager's strongest attributes. But starting on the wing against City, he managed just two efforts at goal - none of which hit the target.

The England international still had some influence on the match, coming inside and often beating right-back Pablo Maffeo for pace, but with Zlatan Ibrahimovich out of form, last night should have been Rashford's chance to clock up some minutes at centre-forward.

Man City are amid a mini-crisis

Manchester United v Manchester City - EFL Cup Fourth Round

We always knew English football would be the toughest test of Pep Guardiola's career and that's already proving to be the case - going win-less in six for the first time as a manager.

Make no mistake about it, Manchester City now find themselves amid a mini-crisis. They've conceded twelve goals in six games, without keeping a single clean sheet, and aren't producing at the other end, scoring just five times. They didn't even record one shot on target against the Red Devils.

If Jose Mourinho were enduring such a stretch just a matter of months into his Manchester United reign, the whole world would be going mad with accusations of the Portuguese losing his way, his passion for management and becoming outdated.

Simply because there's less attention on City shouldn't take away from the fact the club are amid a mini-crisis. A visit to the Hawthorns on Saturday, to face an attritional West Brom side, won't be easy either.