It will be remembered here as the day Dan James staked his claim to be part of Great Britain’s sprinting team for the 2020 Olympics. The 21-year-old was unplayable as his breathtaking pace turned this FA Cup tie on its head and took Swansea into the quarter-finals for only the fifth time in their history.

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It is incredible to think that Swansea were close to allowing James to join Leeds on loan on deadline day. Swansea pulled the plug on that deal at the last moment and, on this evidence, James will have plenty more suitors than Leeds come the summer and be commanding an eight-figure fee in the process.

It was surreal to watch at times as the Welshman tormented Brentford with his lightning speed time and again, so much so that three yellow cards were awarded for bringing him down and Ezri Konsa received a straight red for a professional foul on him. James was also involved in three of the four goals, including an outstanding individual effort, when he ran 85 yards with the ball, leaving a trail of Brentford defenders in his wake, before coolly finishing.

By the time he departed in injury-time, to a standing ovation from the home supporters, Swansea were 4-1 ahead and there was a tangible buzz around the stadium and a clear sense that the crowd had witnessed something special.

“Dan was OK, wasn’t he?” said Graham Potter, smiling. “If you are talking about the ability to sprint repeatedly, it’s as high a level as you will see. He’s got lots to work on. But he had an end product as well today and I thought he was sensational. I was a full-back myself and I’d have probably got a yellow and a red, to be fair. It is a concern [the fouling] but that’s the referee’s job to deal with that. Dan’s courage is incredible, to not only have the ability to do it but to ride the challenges.”

It does seem extraordinary that Swansea almost let James move to Leeds for a deal that was unfathomable in so many ways. Leeds proposed paying a £1.5m loan fee, with no payment until the summer, and £7m to follow in three instalments if they won promotion. It was dangerously close to the transfer deadline when Swansea saw sense and walked away.

Asked how James has handled that situation since, Potter replied: “He’s been top. These things happen in transfer windows and ultimately the clubs didn’t agree the fee and you can see why on that performance. The [financial] numbers were too low, that’s the reality in my opinion. When that happens he just gets on with being a footballer and he’s been incredible for us. We’re looking forward to working with him in the future.”

Potter went on to make the point that, if James does move in the summer, it should be to the Premier League. There will certainly be more and more scouts in attendance after this display. “There were a few instances, not just the goal, and it’s just off-your-seat stuff, like ‘wow’,” said Potter, who is not the sort to get carried away.

It was a strange game in many ways, not least because Brentford were totally in control up until half-time and by far the superior team. Ollie Watkins had put them in front with a lovely finish at the end of a terrific counterattack and it is a measure of how poorly Swansea played in that opening 45 minutes that there were boos from the crowd at half-time.

The mood soon changed after the interval. Bersant Celina’s free-kick, after James was brought down, struck the near upright, cannoned off the back of Luke Daniels, the Brentford goalkeeper, and rolled over the line. Four minutes later Swansea had a second after James blocked Neal Maupay’s pass just outside the Swansea area, knocked the ball out of his feet and set off on that exhilarating goal-scoring run that took him from one end of the pitch to the other.

By now Brentford had lost their way. Thomas Frank, their manager, was booked for trying to stop Oli McBurnie from taking a quick throw and Konsa was sent off for hauling down James in full flight. Celina made it 3-1 when he wriggled past a couple of half-hearted challenges before curling a shot beyond Daniels. Then George Byers, after a neat exchange between James and Celina, stroked home the fourth. “We made a few individual mistakes that got punished unbelievably hard,” lamented Frank.

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Facebook Twitter Pinterest Swansea City’s Bersant Celina (right) celebrates scoring his side’s third goal against Brentford. Photograph: Nick Potts/PA