Spurs host Stoke at White Hart Lane having beaten Greek side Asteras Tripolis in the Europa League on Thursday night.
That 2-1 win, however, was far from convincing - and the 27-year-old believes Tottenham need to cut out silly mistakes if they are to have any chance of beating the Potters.
"It was strange because we didn't win second balls," Vertonghen is quoted as saying by Sky Sports.
"That team can play and the most important thing was they felt they could do something against an English team.
"Of course, we won - but it was not that positive, so we have to analyse this game and see where it went wrong. Then we have to continue and avoid making those mistakes in the next game.
"That's what we have to do against Stoke, because if we make these mistakes against Stoke probably we will lose this game."
Tottenham head into the game in eighth place in the Premier League table, with the Potters back in 13th. Mark Hughes' side are only two points behind Spurs, however.