Spurs were slow to get going against Chelsea on Saturday, conceding an early goal to Gary Cahill.
Vertonghen thinks that Spurs let themselves down by failing to focus from the outset against their London rivals.
He told the Daily Mail: "At home we seem to play better in the second half than the first.
"We need to think about how to put two strong halves together and work out how to put a bit more pressure on teams from the start.
"Chelsea are a good team but I feel we should have done better."
The Belgian international has shown his versatility in his short time in the Premier League, playing in both central defence and at full-back since moving to Spurs from Ajax this summer.