"What a couple of years they've had," Redknapp told the Spurs website.
"Darren Ferguson's done a fantastic job there, absolutely brilliant. He's his own man as well, you know that when you speak to him, he's very focused on what wants to achieve and has a bright future.
"Barry Fry's also there and he's a good friend of mine. It will be a great game for us. They are a good side on a fantastic run. The club is on the up."
Harry fancies Posh to maintain their Championship status. "It will be a lot harder for them in the Championship, it's a big step up and it's a tough league again next season but I'm sure they will survive.
"It's a club with momentum, not a club on the way down and that's means a lot going into the season."