One of several sides bunched together at the top of the table, Tottenham currently sit seventh, five points behind leaders Arsenal and one ahead of City.
However, Vertonghen is not deceived by the relatively lowly position of Manuel Pellegrini's men and believes the 2011-12 champions remain the biggest threat.
"It's really crazy," he told Sky Sports News. "I think if we'd won against Newcastle (prior to the international break), we'd be joint second now - but we're seventh.
"City, I think, is the best team in the league. Arsenal are doing very well of course. But, especially in home games, City is the team to beat."
Tottenham’s next two league fixtures are against the Manchester clubs.
They visit the Etihad Stadium on Sunday before hosting Manchester United the following weekend.
"It's unbelievable how we play City and United next," Vertonghen added.
"It's very hard this year. (Vincent) Kompany (Manchester City's captain and an international team-mate of Vertonghen) already said it will be the toughest league in years to finish top.
"We have to be at our best to finish in the top four."
