Oxford United were 1-0 down at the break, with Sibley, making his first league start for the U’s, booked for a rash challenge on Swans captain Matt Grimes.

United introduced Idris El Mizouni for Sibley at half-time in an attempt to wrestle control of the midfield battle and get higher up the pitch.

It almost paid off immediately when El Mizouni collected a pass through from Tyler Goodrham and crossed from the left-hand side for a stretching Mark Harris, who sent his effort off target.

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U’s head coach Buckingham said: “I just wanted to try and get a hold of the midfield a little bit more, and Louie was on a booking.

“It was the first start for him, and not necessarily anything that he’d done wrong. It was just making sure we could utilise the players we have in our midfield, while keeping everyone available.

“Idris may get on the ball a little bit more and help us drive up the pitch the way he does.”