Spurs were beaten 1-0 at home in the north London derby by Arsenal on Sunday, with a goal from Tomas Rosicky inside two minutes proving enough to secure victory for the visitors, who reignited their title bid.
It was a second Premier League defeat on the bounce for Spurs after their 4-0 loss at Chelsea and leaves Tim Sherwood's side fifth in the table and seven points behind Manchester City, who have three games in hand.
It would now be a tall order for Spurs to close such a deficit over their remaining eight league games and they look likely to miss out on the UEFA Champions League placings once again.
"I do not want to look at the table any more because the gap (to the top four) is very big," said Vertonghen.
"All four sides at the top are stronger than they were last year and we have stayed at the same level. If you see last season, then we did not improve.
"I think we do have the players to achieve Champions League (qualification) and I hope we can achieve it next year."
And the Belgium defender knows his club have little time to dwell on their missed opportunities against the Gunners as they have to face the second leg of their Europa League tie away to Benfica on Thursday night, in which they trail 3-1.
"Of course we are all disappointed but we will try to come back with some good results," Vertonghen said.
"It is difficult now but we have to (pick ourselves up) and go again."
Full-back Danny Rose also voiced his disappointment over the possibility of finishing outside the top four after such a positive start under new manager Sherwood.
"Once the manager took over in December, we were on fire and we have had a bad week where we have become detached from the top four and it is hard to take," Rose said.
"It is going to be very hard to break in this season. We might have to look to next season now, regroup and see what happens.
"Some of the games we have lost at home and drawn at home, it has been unacceptable - Tottenham of two or three seasons ago were beating these teams comfortably.
"It is something to look at and we're definitely disappointed that this season may go again without finishing top four.
"Against Arsenal is the best we have played in a very long time, but the difference between the top four and the teams below, is once they get a chance, they take it."