Manchester United took a giant step towards the Europa League final with a 6-2 drubbing of AS Roma in their semi-final first leg at Old Trafford on Thursday.

United's run of four semi-final losses under manager Ole Gunnar Solskjaer should be ended after next week's second leg in the Italian capital after Bruno Fernandes and Edinson Cavani gave a display of class, providing two assists each to go with their goals.

Roma paid the price for three first-half injuries, including goalkeeper Pau Lopez, which forced them to use all three substitute windows before going in 2-1 up at the break.

But that should not disguise the impact of the quality provided by Fernandes and Cavani which the visitors simply had no answer to.

It wasn't quite a repeat of United's 7-1 win over Roma in the Champions League last eight in 2007, but it should give Solskjaer a chance to secure his first silverware as manager.

"I don't feel the job is done. We did a good job and did well but we know they have quality," said Solskjaer.

His counterpart Paulo Fonseca, however, was left puzzled how a team that was leading at the break could have fallen apart so badly.

In the other semi-final on Thursday, Villarreal claimed a narrow advantage against Arsenal with a 2-1 home victory, although they will feel frustrated at letting the London club off the hook.

First-half goals by Manu Trigueros and Raul Albiol put the Spanish club in command and it looked bleak for the visitors when Dani Ceballos was sent off just before the hour mark.

Arsenal were rocking and needed keeper Bernd Leno to avoid them slipping further behind but they were thrown a lifeline when Nicolas Pepe converted a 73rd-minute penalty.

The chaotic game took another twist as Villarreal were also reduced to 10 men when former Tottenham Hotspur player Etienne Capoue received a second yellow card.

Villarreal, coached by former Arsenal manager and Europe League specialist Unai Emery, maintained their 100 percent home record in the competition this season.

But the tie remains delicately balanced ahead of next week's return in London.