A dry opening half resulted in fewer scoring chances, with each side reduced to shots from range, with Marcus Rashford firing at John Ruddy on 14 minutes.
"Sometimes it's centimetres and they spend three minutes on VAR looking at it, imagine taking the decision in one second during the game".
Swansea players were unhappy when Cameron Carter-Vickers was judged to have tripped substitute Raheem Sterling for the equaliser, while Sergio Aguero was offside when he headed in the victor two minutes from the end.More news: Downstream Missouri River prepares for flooding
Aguero had the last laugh, however, when he headed his 28th goal of the season in all competitions, although he appeared to be offside and the Video Assistant Referee (VAR) system was not being used in the match to the dismay of the Swansea fans.
"We will analyse the game - we deserved to win the game by far - but to win in that way, I'm sorry".
From then on in it was all Manchester City and an own goal off the back of Swansea goalkeeper Kristoffer Nordfeldt after substitute Sergio Aguero's 77th-minute penalty had hit the post levelled the tie.
Swansea said the club was set up to use VAR given their history of being in the Premier League between 2011 and 2018.More news: Australia's 2-year ODI losing streak ends in New Delhi
Had VAR been applied to non-Premier League stadiums in the FA Cup, the visitors' second and third goals would not have stood.
United never convinced and could have lost by more, with Sergio Romero turning Jimenez's header on to the bar and denying Jota. "The performance was one to be very proud of". "We had composure, shape, good running", said Wolves manager Nuno Espirito Santo.
"I'm here until the summer, we've got loads to play for in the league and the Champions League".
Javi Gracia's side had taken the lead through Etienne Capoue's first-half strike before Michy Batshuayi equalised for Palace after the interval.More news: Bracketology: Where Louisville stands after wild ACC Tournament