A near full-strength United struggled to break down resilient Hull in a first half in which the hosts had just two shots on target - Mata forcing a good save out of goalkeeper Eldin Jakupovic, who also tipped over Paul Pogba's long-range effort.

The visitors had chances of their own against a side who had won their eight previous games in all competitions, Robert Snodgrass causing problems from set-pieces.

However, Mata got the breakthrough just before the hour mark when he tapped in from Henrikh Mkhitaryan's knockdown.

Substitute Fellaini scored a second late on, heading in from Matteo Darmian's cross to put United in command heading into the second leg on 26 January.

Serious business for Mourinho

The League Cup represents a genuine opportunity for Mourinho to claim a major trophy to add to the Community Shield collected last summer.

He has named strong sides throughout the competition and it was no different against Hull as several first-team regulars, including Wayne Rooney, Pogba and David de Gea, started.

With Hull bottom of the Premier League and struggling badly with injuries - they could only name six substitutes - a first Tigers victory in 65 years at Old Trafford seemed unlikely.

They were given odds of 20-1 to win before kick-off and their prospects looked even more bleak when midfielder Markus Henriksen went off injured inside 20 minutes.

But since new Portuguese boss Marco Silva - described by some as the new Mourinho - took charge last week the Tigers have looked much improved. They beat Swansea in the FA Cup at the weekend and more than held their own for long periods of the game against the Red Devils despite having to field a makeshift defence.

Fellaini's late goal means a turnaround in the second leg might be too big a challenge, but their overall performance will give their fans hope in the battle to stay in the Premier League.

Rooney moved level with Sir Bobby Charlton at the top of Manchester United's all-time scoring chart with his 249th goal for the club against Reading in the FA Cup on Saturday, meaning he had the chance to claim the outright record against Hull.

He came close to scoring goal number 250 inside the opening 10 minutes when Marcus Rashford scuffed a shot across goal, but Rooney was just beaten to the ball by Andrew Robertson.

The England forward should have got the landmark goal just after half-time when he was picked out by an excellent Pogba ball over the defence, but sent his shot wide of the far post.

His game came to an end just before the hour mark when he was replaced by Anthony Martial, but his departure without a goal means he now has the chance to grab the historic strike in what is arguably a more significant fixture for himself and United fans - the visit of Liverpool this weekend.

What they said:

Manchester United boss Jose Mourinho: "Maybe I didn't prepare the team right. I didn't give them enough intensity, and we had to change that at half-time. Maybe I should pay more attention to the dynamic of the game.

"We have to improve for Sunday. Today our performance was enough to win, but Sunday we all have to improve."

More from Mourinho here.

Hull City manager Marco Silva: "There's only been four training sessions with me and with many, many things to change, I'm happy with the work my players did during this game."

Red Devils' run continues - the stats

Manchester United have won their past nine games in all competitions, their best run since an 11-game winning streak in February 2009.

Juan Mata has scored in three of his past four League Cup matches (two goals for Manchester United, one goal for Chelsea).

All three of Henrikh Mkhitaryan's assists for Manchester United have been in the EFL Cup.

Marouane Fellaini has scored his first League Cup goal since August 2013 (Everton v Stevenage).

The Red Devils have progressed from all three of their previous League Cup semi-finals having won the first leg (1983 v Arsenal, 1991 v Leeds, 1994 v Sheffield Wednesday).

United have won 12 and lost none of their past 13 matches against Hull City in all competitions (D1).

The Red Devils have lost only one of their past 26 home League Cup games against fellow top-flight sides (W24 D1), losing 2-1 against Chelsea in January 2005.

Hull have failed to score in each of their past four matches with United, losing three and drawing the other.

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