He said: "When we promoted the time before, we had no money to spend.
Whitehead added: "It has been a difficult start, but we had some tough games in that spell.
"The Reading game was a big one and we won that, and we have to kick on again now."
Whatever happens in north London this weekend, Whitehead will continue his own mission to get back to playing football having decided not to leave after the club's most recent ignominious relegation.
He said: "When you get relegated and you have played in the Premier League, you want to stay there and play against the best players.
"Of course you will be tempted, but I knew what the potential of this club was and we are starting to get there now."