Pompey had looked for large parts of the game at the City Ground that they would be the first side in over a year to inflict a home league defeat on Billy Davies's side but were undone by two goals at the death.
Cotterill remains under severe financial constraints at Fratton Park and lamented afterwards: "If we had had their bench we would have seen that game out ... 100 per cent certain we would have done that. But we can't bring on the kind of players that Forest have at their disposal."
Davies unsurprisingly saw things slightly differently and said: "Portsmouth are a Premier League club with Premier League players and salaries and it showed with the way they played against us.
"Like ours, their squad is on the small side but they made it very difficult for us today."