Manchester United's top four chances suffered a heavy blow with a 2-1 defeat at Wolves on Tuesday night.
Scott McTominay's low strike from 22 yards - his first goal for United - put them ahead after 13 minutes but the hosts equalised 12 minutes later as Diogo Jota coolly finished from a Raul Jimenez pass.
The visitors had captain Ashley Young sent off in the 57th minute for two yellow card offences after he twice fouled Jota inside a five-minute spell.
Wolves took advantage as they scored a scrappy second goal when David de Gea failed to collect the ball and it ricocheted off United defender Chris Smalling and into the net to give the hosts the win.
The defeat was the first under Ole Gunnar Solskjaer since he was given the United manager's job on a full-time basis and left them fifth in the Premier League.
United are level on points with fourth-placed Tottenham and two points behind Arsenal in third, but have now played a game more than both London clubs.
Wolves boss Nuno said: "Tonight was a good night, a good game of football.
"What more can you ask? We know it was very difficult. The extra effort the boys make and they the react to the first goal - I'm really pleased.
"I give credit to United for how they shaped themselves, it was difficult to recover the ball. The way we reacted was amazing.
"Even after the red card it is always difficult against United. We created spaces and had more chances. If there's one thing I can complain about it is being more clinical.
"The preparation starts now for the semi-final - we will rest and prepare for a difficult game. A fantastic challenge for us."