Manchester United won their fifth straight game under caretaker manager Ole Gunnar Solskjaer as they beat Reading in the FA Cup – but there was VAR confusion in the first half.
Fred’s goal was ruled offside but United were awarded a penalty for a foul on Juan Mata in the build-up.
The Spaniard scored from the spot, before Romelu Lukaku doubled their lead just before half-time.
The draw for the fourth round is live on BBC One on 7 January.
It was unclear to many what referee Stuart Attwell was checking when he called on the video assistant referee in the 20th minute.
Alexis Sanchez had chipped the ball to Fred on the edge of the box to control it with his chest and pass to Mata, who then poked the ball through for the Brazilian to slot home.
The assistant referee flagged for offside against Fred before Attwell then went to VAR – and a three-minute delay followed.
Replays showed Mata was actually caught by Omar Richards before he had played the ball and eventually a penalty was given.
A message saying “VAR check in progress, checking penalty” flashed on the screen, but for those watching on TV at home and the Old Trafford crowd confusion still reigned.
“I was quite sure it was a penalty on me,” Mata told BT Sport. “It [the VAR] took longer than normal hopefully be quicker in future, but it was the right decision.”
Solskjaer said the foul on Mata was “clear and obvious and factual,” adding: “I didn’t need VAR to see that Mata was fouled.”
“The use of VAR was questionable there – it has got to be quicker,” said former United defender Phil Neville. “In defence of Jon Moss – the fourth official – there were a lot of mitigating factors there.
“The three or four-minute delay made a sense of uncertainty at Old Trafford – even though the right decision was made in the end.”
BBC Sport’s Simon Stone added: “For the fans inside the stadium who could only see the referee and players at a distance, it was a bit frustrating judging by the whistles and jeers.
“I don’t think the time taken is an issue – if the fans know what is going on.”
United form drops
United’s free-scoring form of recent weeks was missing, while Reading, who are second from bottom in the Championship and appointed manager Jose Gomes at the end of last month, had the better chances.
But for their finishing and play in the final third, the visitors would have made this a much tougher test for their Premier League opponents.
Sergio Romero stopped a powerful effort from Andy Yiadom in the first half and made a good save with his legs to deny Callum Harriott just after half-time.
Harriott was a constant menace to the hosts’ defence, while Liam Kelly was dominant in midfield.
“They beat us but they didn’t take our confidence,” said Gomes. “We are a second division team but we played face to face with Manchester United. It is a big hope for the future.”
Lukaku showed glimpses of recovering last season’s scoring form and took his goal well, timing his run to latch on to Sanchez’s through ball and rounding Anssi Jaakkola before slotting home for his third goal in three games.
Sanchez, making his first start since November after recovering from a hamstring injury, did not look yet back to his best and lasted just over an hour before coming off with an injury.
The Chilean indicated he had an issue with his hamstring as he walked off and then accidentally sat in Solskjaer’s seat – before the Norwegian asked him to move.
United, who made nine changes from their 2-0 league win at Newcastle looked slow and disjointed.
They improved with the introduction of attacking substitutes Marcus Rashford and the lively Tahith Chong, a 19-year-old academy product who was making his first-team debut.
But they only had a couple of chances in the second half – substitute Marouane Fellaini seeing a weak effort saved and Jaakkola keeping out Andreas Pereira’s shot at the end.
United now head to Dubai for warm weather training before facing Tottenham in the league on 13 January (16:30 GMT kick-off).
Before Saturday’s game, Solskjaer said it was an “opportunity for everyone to put themselves in the frame” to face Spurs.
Based on this performance, there will be wholesale changes for when United travel to Wembley.
“The way we played wasn’t the best,” said Solskjaer. “We made nine changes, so I made it hard for the boys because they hadn’t played together too much.
“But we got the goals and managed to get through.”