Luke Shaw felt Manchester United had to overcome an "awful" first half to defeat Milan 1-0 and seal their place in the Europa League quarter-finals. 

The last-16 tie was finely balanced after a 1-1 draw at Old Trafford in the first leg, with the hosts looking the more likely scorers in the opening half of the return fixture after United's bright start had quickly fizzled out. 

However, Paul Pogba's introduction for the second half proved decisive, the substitute firing in the only goal of the game in the 48th minute at San Siro. 

Shaw was delighted to see Pogba back in action again after missing 10 games through injury, but acknowledged Ole Gunnar Solskjaer's side must improve as they look to secure silverware this season. 

"Obviously very happy we're through, but I'll be honest – and I think the lads and the staff will agree with me – we weren't good at all, especially in the first half when we were awful," Shaw told BT Sport. 

"In the first 10 or 15 minutes we started well, kept control of the ball. But it was like a switch – we turned off and were very sloppy.  

"We kept giving away balls and bringing pressure on ourselves. We were lucky, but then second half it always helps when you have a world-class player like Paul to come on and make a difference.  

"He did that - it's brilliant to have him back. The most important thing tonight was the result and getting through to the next round, no matter how we played.  

"But we know we need to be better than tonight."

United have progressed from each of their last two knockout ties with Milan in European competition, though they needed a fine save from Dean Henderson to deny Zlatan Ibrahimovic an equaliser.

Next up is an FA Cup quarter-final against Leicester City, the Red Devils travelling to the King Power Stadium on Sunday.

"Obviously, Milan are a top side and we knew it would be hard, especially coming here. The result wasn't in our favour [from the first leg], so it's a very good win," Shaw continued.

"The most positive [thing] is we are through and have got players coming back. The squad is looking much better than it did last week, so it’s good times now. 

"Hopefully we can push on, because we've got a big game around the corner at the weekend."

After cup duty at the weekend, Shaw will join up with the England squad. He has been recalled by national team boss Gareth Southgate for the upcoming World Cup qualifiers against San Marino, Albania and Poland, just reward for his outstanding form at club level.

"I'm extremely happy – it's a massive honour to get selected for your country," the left-back said.

"Obviously, I’ve been out of the fold for quite a while, I’ve had ambitions to get back into the squad. Luckily I’ve done that, so I just need to keep going."