The Fulham number one is concerned that what has been an excellent, if somewhat unexpected, start to the Premiership season could all go pear shaped should the Cottagers get a few injuries and suspensions.
"Our season will hinge on how many injuries and yellow cards we pick up," the Holland international told the Evening Standard.
"We haven't got the biggest squad and definitely need to strengthen in January. We've got a few injuries to strikers at the moment so are a bit limited.
"We're not that strong up front and could do with more options. We have missed Luis Boa Morte because with his pace he can create something out of nothing, but we have to do it with the players we have fit."