He told the club's official website: "I just felt it was too good an offer for the club to turn down.
"I thought it was the right time in terms of the finances that we get from this deal. But, for the bigger picture of everything this will bring in terms of strengthening the finances for the next couple of years, it is a really good deal for Frecklington as well.
"You look at his form this season and it's been up and down, people can't say we've lost a brilliant player, we've lost a player that has been a little bit inconsistent and Frecklington knows that and I know that. But obviously now he's playing with better players and better standard of football and he has to be up to the mark each week and not have one good game and then one average game.
"And I don't feel I've seen the best of him, people talk about when he was here under (John) Schofield and what a good player he was, but since I've been his manager he's been a little bit inconsistent, but that's by the by now. Lee's a Peterborough player and our best wishes go with him and hopefully it will work out for him."