Harper said: "Chelsea have to come to win. After a crucial game in the Champions League, it is yet another huge one for them. But this is our final home game of the season and we want to give our fans, who have supported us so well this season, a really good send-off.
"Everyone in Manchester will be willing us on. We are all fully aware of just what a massive game this is and its implications. Last season I remember Titus Bramble smashing into Michael Ballack after 25 minutes. I don't think he's been back too long since that tackle.
"We managed to keep a clean sheet that day and will be looking for more of the same, plus grabbing the win.
"At Stamford Bridge in December we were only undone by a poor offside decision in a 2-1 defeat and the rot set in soon after that.
"Losing that day set us on a terrible run for almost three months. Yet they know we gave them a really good game and it will be more of the same this time.
"It's advantage Manchester United, though. They have a superior goal difference, which is like a one-point lead. Even so, it's fantastic. Football fans love to see a close title race."