Wigan's FA Cup defence got past the first fence but only just after an enthralling third-round tie.

With a new cast and a different manager at the helm, they were unrecognisable from the team that defeated Manchester City at Wembley eight months ago and were thankful for a penalty save from Ali al-Habsi to earn them a replay with League One side MK Dons next week. Uwe Rösler, the second successor to the legacy left by Roberto Martínez, was relieved to get that opportunity.

"We now have to show how much as a club we want to defend our title," he Rösler. "Several of my players, coming from the Premier League, underestimate League One players. You can't do that. I have been long enough there to know there is no difference, the difference is in wages."

Ben Watson, scorer of the most famous goal in Wigan's 82-year history, was missing with a foot injury and of those who have remained since Premier League relegation, only five of last May's heroes started. Two of those registered on the scoresheet as the Championship side dominated the opening half-hour: Roger Espinoza drilled in a 30-yarder and Jordi Gómez tucked inside the near post as a result of Wigan's pressing game winning the ball deep into opposition territory.

Yet from a position two goals to the good and cruising towards the fourth round, Wigan were rocked by two Ben Reeves goals on the stroke of half-time that provided the contest with a new complexion. First, a fluid passing movement from the right incorporating the substitutes George Baldock and Samir Carruthers culminated in Reeves wedging a left foot effort into the bottom corner.

Then, when top scorer Patrick Bamford – the on-loan Chelsea forward who will return to Stamford Bridge before a temporary switch to Derby – wriggled free down the left, Reeves was there to convert the centre with the aid of a deflection.

Having drawn level from nowhere, Karl Robinson's bright young things threatened to turn the game on its head on the hour when a raid down Wigan's left flank resulted in Baldock being felled by James McClean's clumsy challenge. But Shaun Williams's penalty lacked conviction and Habsi repelled it with ease.

When Callum McManaman latched on to Espinoza's dink over the visitors' defence to restore Wigan's advantage five minutes later, it appeared the balance of power had been restored. But it simply reinvigorated the men from Milton Keynes.

The portents for a Bamford leaving present were good – he once scored four for Nottingham Forest against Wigan in an FA Youth Cup tie and also breached Wigan's defences in one of his early appearances for Chelsea's reserves – so it was no surprise when he popped up to poach the equaliser inside a crowded penalty area eight minutes from time. Unfortunately for MK Dons, he will not be around for what promises to be a fraught replay.

"Everybody can see how this young boy has developed. There weren't many takers for him four months ago but 17 goals on, everybody wants to talk about him. He will be a top player and I am proud to have been able to work with him," said Robinson."They will come at us harder, quicker and with a lot more quality and determination, so we will have to be even better than we have been here."