Nugent is battling for his future on the south coast and Redknapp said: "I wasn't happy with our first half performance and in the second we needed to score when we had a great chance with us well on top.
"But David has missed it and then Pedro Mendes gives the ball away and it is game over. Is David lacking confidence?
"Possibly, but it's the first time he's played at this level and not been an automatic choice.
"It is disappointing because I would like to have had a Carling Cup run but would I swap our with at Blackburn in the league last month for a win against them in the cup? Not really."