Hull will play the first leg of their last-four tie with the Red Devils in Manchester in the week commencing January 9, with the return leg taking place at the KCOM Stadium around a fortnight later on the week beginning January 23.
The mouth-watering prize for Hull in their first-ever appearance in the last four of the competition affords plenty of sentiment to Phelan, who won the competition as a player with United in 1991-92 and was assistant to Sir Alex Ferguson during the final successes over Tottenham Hotspur and Aston Villa respectively in 2009 and 2010.
Manchester United swept past West Ham last night, 4-1 at Old Trafford, with Zlatan Ibrahimovic and Anthony Martial both on target twice.
The other semi-final sees Southampton – who won 2-0 at Arsenal last night – take on Liverpool.
Hull have not beaten United in their last 12 matches and you have to go back to November 1974 for their last victory – a 2-0 win in the old Division Two at Boothferry Park, thanks to goals from Alf Wood and Ken Wagstaff.
You need to go back much further to their last success at Old Trafford, a 2-0 FA Cup win in 1952, with United winning 6-0 on aggregate in their only previous meeting in the League Cup in a round-two tie in 1987-88.
On his thoughts on the tie, United boss Jose Mourinho, speaking after his side’s emphatic quarter-final win over West Ham, said: “I am sure that Hull City has an amazing memory from Wembley (Championship play-off final) last season and that they are going to try everything to be there again.
“We were there last season and there in August and Manchester United is used to being at Wembley on a regular basis, so we are going to try (again).”
United triumphed 1-0 at Hull in the Premier League in late August, thanks to Marcus Rashford’s last-gasp goal and the pairing means that the Tigers will face Mourinho’s side three times in just over three weeks – with a league fixture at Old Trafford scheduled for February 1.
Hull became the third White Rose side in five seasons to reach the League Cup last four following Tuesday night’s dramatic penalty shoot-out win over Newcastle United.
In the process, they made a piece of history by booking a semi-final berth for the first time in the competition’s 56-year history and their aim now to seal a historic final spot and become the county’s first finalist since Bradford City in 2012-13.
Heralding a historical progression to the semi-finals, Phelan said: “For this football club, it is a tremendous achievement.
“This is the furthest its ever been and the players are really pleased for that because it gives them something in Rothmans now. They can say they have got to a semi-final of this competition and hopefully they can go one step further.”
Hull’s progress to the last four will mean that they will play at least 12 games in a busy seven week spell, with the possibility of another addition if they are involved in an FA Cup third-round replay next month.
The congested programme is likely to heighten the Tigers’ need to bring in additional recruits in the January transfer window, with Phelan’s options already far from plentiful for a key final month of 2016.
Elsewhere, Southampton outclassed a much-changed Arsenal side to seal a comfortable victory at the Emirates Stadium and secure an EFL Cup semi-final berth for the first time in 29 years – and a semi-final tie with Leeds United’s conquerors Liverpool.
Arsene Wenger made 10 changes to his team from Sunday’s win over Bournemouth but Saints were good value for their 2-0 win. The visitors, showing eight changes of their own, eased through as Jordy Clasie’s goal was followed by a smart Ryan Bertrand finish as Claude Puel’s men wrapped up the win before half-time.