Posh goalkeeper Joe Lewis will miss the rest of the season after fracturing his kneecap in the 3-2 defeat to the Dons on Sunday.
Paul Jones will come in to play in goal whilst Charlie Lee is suspended having been sent off in the first leg.
Manager Darren Ferguson is hopeful that Grant Basey will have recovered from an ankle injury in time to fill in at left-back for Lee.
He said: "Grant's fine, he's trained for over a week, he was a couple of sessions short for Sunday.
"We've got him to choose or Tommy Rowe could play there, I have got options, it's been a position that's been a problem most of the season."
Gabby Zakuani is also expected to recover from a shoulder injury to face the Dons for a place in the play-off final.
MK Dons will have midfielder Stephen Gleeson available for the return leg of their play-off semi-final at Peterborough after the Football Association rescinded the red card he received in the Dons' 3-2 win on Sunday.
Manager Karl Robinson welcomed the FA's decision. He said: "It's great news. We all felt the FA would make the correct decision and I am glad that it has gone through the right avenues.
"People can make mistakes in every walk of life and a mistake has been made, but it has been rectified which is great.
"Stephen has been in fantastic form all season and he deserves his chance to get this club into the final."
Midfielder Peter Leven will again miss out for the visitors due to a broken foot, with Adam Clayton again set to deputise.
Luke Chadwick's arm injury is not as bad as first feared so he should feature in what is expected to be an unchanged starting 11.