Many in the biggest crowd of the season at this ground probably came to admire Manchester United's gilded youngsters. But while they would have enjoyed watching Ravel Morrison, Ryan Tunnicliffe and company, most of them would have left praising an impressive Sheffield United side, led by the dangerous Jordan Slew. Few in the near 30,000 crowd would have been willing to predict the outcome of the second leg at Old Trafford on Monday.

While Paul McGuinness's Manchester United team are looking to win a record 10th FA Youth Cup for the club, Sheffield United hope to lift the trophy for the first time. They recovered well from a slice of early misfortune here – the visitors seemed too astounded to celebrate when they were awarded a goal after the ball did not appear to cross the line. It looked as if Jesse Lingard's header had been cleared by Harry Maguire but after consultation the officials saw things differently.

If that left the visiting players happily puzzled, John Pemberton's Junior Blades were angrily mystified. Initially slapdash in possession, they drew level just before half-time when the excellent Callum McFadzean collected the ball on the halfway line and ran at the Mancunian defence. He then directed a terrific, dipping 25-yard shot into the bottom corner.

Although Tunnicliffe's eye-catching central-midfield authority, alongside the powerful if sometimes less than sweet-passing Paul Pogba, had caused Sheffield United problems, five of Pemberton's team had experienced Championship football with the Bramall Lane seniors this season. Such experience, in players who will be expected to form the nucleus of next season's League One first XI, helped to subdue Morrison, Manchester United's key creator. Deployed just behind his team's principal striker, Will Keane, Morrison showed glimpses of his exciting ability but sometimes struggled to bypass the commanding Maguire and intelligent Terry Kennedy.

A Tom Huddlestone-sized 18-year-old centre-half, Maguire is a minor cult figure in South Yorkshire, having dumped Craig Bellamy on his backside three times while making his senior debut against ­Cardiff in April. Slew also has senior ­experience and, following a slow start, the striker did well to shrug off Pogba – a ­midfielder in the Patrick Vieira mould – and unleash a shot that was tipped expertly to safety by Sam Johnstone.

Morrison very nearly restored ­United's lead but his curving shot was saved splendidly by George Long. The Sheffield United goalkeeper made some stellar saves but he was beaten when, breaking smartly once more, Pogba played in Lingard. His cross was lashed home by Will Keane.

Undeterred, Slew, whose change of pace and habit of pulling out wide was causing consternation in the visiting defence, promptly and slightly ­fortunately ­equalised, thanks to a heavily deflected 20-yard shot.

"Manchester United's players are all 6ft-plus, all strong and can go past ­people but we've still got a chance," said ­Pemberton. "We're going to have to really perform at Old Trafford but I'm fantastically proud."