The Dutch forward, 27, feels Arsenal have the strength in depth to beat Leeds and secure a home fourth-round tie against Huddersfield.
He said: "Those two cup games were not good enough, but against West Ham, everyone played really well and were fighting for each other.
"This game is vital because we have a big chance. If we win against Leeds, then it will be a game against a lower league side again.
"I have looked at the draw, there are a lot of other Premier League teams playing each other, which means we have big chances to make progress.
"We have the squad to go further because 90 per cent of the players are fit and we can rotate a bit when needed."