Team news from Barnsley and Sheffield Wednesday that will interest Posh boss Darren Ferguson and the club's fans
Barnsley have already qualified for those play-offs and they will tackle either Bolton Wanderers or Derby County away from home in a first leg tie on Saturday, May 13.
Duff dismissed concerns about momentum with his side picking up just one point from their last two matches. He was disappointed with his side’s 4-4 draw at relegation-haunted MK Dons last weekend.
"Sunday is a good game for us,” Duff said. “The fact that Sky are here and Peterborough have got everything to play for, but it is not going to dictate our season.
“The focus has not really changed. We will try and win and give it our best shot, but like last Saturday, if there is a 50-50, then I am not taking a risk with anyone.
“People talk about momentum, but we have had momentum for six months. Anyway we didn't lose last week and had all the momentum at the end of the game.
"I don't worry about how other people dress things up. Everything that the staff give the players comes from a good place.”
Barnsley are sweating over the fitness of key defenders Mads Andersen and Jordan Wililams, who have both have injury issues ahead of Sunday's game.
Andersen missed MK Dons match with an abductor issue and Williams has a slight hamstring injury. Both have undergone scans.
Midfielder Luca Connell and Adam Phillips, who have not been involved in the Reds' last two games, are back in training and in contention.
Should Barnsley pick up three points, it would take their season's tally at Oakwell past the half-century mark for the season. They have already recorded 16 home wins, including against Sheffield Wednesday, Plymouth Argyle and Derby County.
"The home record has been really good and we have had a lot of wins and not many draws,” Duff added. “But there have been too many losses for my liking (5)!
"But in terms of how the team has evolved this season - especially at home - is why the atmosphere is better and it's about trying to keep it going now.
"The players understand this as they are not daft. We are at home and are good at home.
"We have to prepare for all eventualities and it is very unlikely that you will play the same team for the next four games."
Posh also received a boost from Sheffield Wednesday manager Darren Moore. Posh have to beat Barnsley and hope they receive help from the Owls in their final game against Derby County on Sunday.
Moore is a former Derby player, but he is keen for his current team to win for the fourth straight game to set them up for a play-off semi-final against Posh or the Rams.
“We stay focused with it and we make sure we’re selecting the best team possible going in,” Moore told The Sheffield Star.
“You want to keep the momentum and keep the focus going. There were elements of the game last Saturday that were comprehensive and rewarding, but there are elements we also want to work on going into this week's game.”
Wednesday have been boosted by the return to fitness of centre-back Micheal Ihiekwe and forward Josh Windass.