Nugent joined Burnley on loan from Pompey on transfer deadline day, bringing a temporary halt to an underwhelming spell at Fratton Park that saw him score just three goals in 34 Premier League appearances following a £6m move from Preston in July 2007.
The 24-year-old, who scored on his only appearance for England, was frequently used as a winger by Portsmouth and has detailed how his morale plummeted when working under Redknapp, who left the club to manage Tottenham Hotspur last season.
Nugent did not feel wanted at Fratton Park and has welcomed the chance to return to the North West, where he began his career with Bury.
"It was horrible," Nugent told the Daily Star. "They're a great set of lads down there but I lost so much confidence with the manager not playing me. When I did play it was as a winger and that was a bit tough. I was there to do a job for the team and I did my best as a winger.
"But everyone knows I am a striker and I need to be up top to score the goals. It all made my confidence go down to its lowest level. Every time I came on as a sub I seemed to make an impression but that wasn't good enough for the manager.
"Everything since I joined Portsmouth has just been downhill. He is a good man-manager but it just didn't seem to work with me. After a few weeks he didn't fancy me as a player and I had to just get on with it."
Following Nugent's arrival, Redknapp quickly admitted that the striker was available for loan. The player added: "It was disappointing to hear that after three games. The first game is always tough in the Premier League and we played Manchester United and then Bolton. It was tough but after three games that was it. That is football. People make mistakes and I made one.
"I was down there on my own with no family but I just had to get on with it. I could have left early on for Derby but I decided to stay.
"The last two years have been tough and I am just glad to get away and hopefully start playing some games. People have been doubting me ever since the first couple of weeks at Portsmouth and I am going to do what I can to prove them wrong and show them what they've been missing.
"It's a relief to get out of Portsmouth. Everyone knows I didn't really enjoy it down south and hopefully I can come back up north now and reproduce the form I showed at Preston."