"I care about staying in the Premier League, as does everybody at this club.
"Our Premier League status is not protected by winning the FA Cup and it is a simple as that.
"It is a fantastic competition and perhaps one day we will be in a position where we can compete for it but not now."
Kitson would not have started anyway as manager Steve Coppell uses cup ties to give fringe players game time regardless of the opposition, and given the Pompey game was the second in three fixtures that the Royals have ended down to 10 men, his first choices are in need of a rest.
Kitson added: "We have just come off the back of some fixtures that have been tightly packed together and we have played almost two full games with 10 men.
"I am absolutely shattered and so is Kevin Doyle and a lot of the other players are as well."