The Blades started brightly and had the first shot of the game as Jamie Murphy flashed an effort wide at the near post, while Steven Davies diverted a cross-shot marginally wide.

They turned their pressure into a goal a few minutes later as Kieron Freeman neatly volleyed the ball past the goalkeeper.

Kieron Freeman of Sheffield United battles celebrates scoring the opening goal during the Sky Bet Championship semi final match first leg match between Sheffield United and Swindon Town at Bramall Lane on May 7, 2015 © Getty Images

Swindon were handed a chance to equalise shortly after as Nathan Byrne earned his side a penalty. However, Ben Gladwin's low effort was saved by Mark Howard.

The visitors continued to push forward and almost found an equaliser just after the break, but Michael Smith's header drifted wide.

However, Sheffield couldn't keep them out for long as Sam Ricketts powered in a header just four minutes later.

Sam Ricketts of Swindon Town scores the equalising goal during the Sky Bet Championship semi final match first leg match between Sheffield United and Swindon Town at Bramall Lane on May 7, 2015 © Getty Images

United almost re-took the lead immediately as the ball found its way to Freeman in the box, but his low drive missed by inches and Davies missed two glorious opportunities late on.

However, it was Byrne who scored the winner as his long-range shot caught out the keeper and nestled in the back of the net.