MK Dons ended a run of four games without a win by inflicting a third-straight defeat on 10-man Walsall.
The Saddlers had veteran goalkeeper Jimmy Walker sent off for handling outside the box, prompting full-back Lee Beevers to go in goal.
He was soon beaten as Dean Lewington curled a free-kick into the top corner.
Jabo Ibehre stabbed in the second after Beevers blocked a shot from Daniel Powell, while a Claude Gnakpa shot hit both posts for the Saddlers.
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MK Dons manager Karl Robinson told BBC Three Counties Radio:
"If we take our chances in the second half, the game goes completely out of their reach. We just didn't take our chances really.
"You can tell they (Walsall) really like playing for the manager here. The way they came out for the second half and the way they got at us was a credit and a testament to them. But our boys stayed strong and got a clean sheet.
"It felt comfortable. I just always felt in control. OK, it wasn't the perfect second-half, but it was three points. It is a fantastic result and we move on from here."