Janssen was the top scorer in the Eredivisie last season with 27 goals, and has also become Holland's main striker at international level.
It is little wonder clubs are interested in signing him from AZ Alkmaar, and the longer Tottenham leave it without making a bid, the more chance there is of other clubs stealing in to sign him.
Vincent Janssen scores the first goal for the Netherlands from the penalty spot
Missing out on him would be hugely disappointing for Tottenham and their fans, but Spurs may be prepared for the eventuality just in case, tracking another Eredivisie striker.
The London Evening Standard reported in April that Tottenham had been scouting FC Utrecht's Sebastien Haller, who is just 21-years-old.
Haller scored 19 goals in the league last season, and a further five in all competitions bringing his tally to 24. His agent Loic Gustan also confirmed interest from Tottenham, and told Calcio Mercato that he would consider his options at the end of the campaign.
Reports of Tottenham's interest has gone a little cold for now, while presumably they focus on attempting to sign Janssen and or Michy Batshuayi.
If a deal for Janssen, 22, falls through it would not be a surprise to see Tottenham make a move for French striker Haller, and still come up smelling of roses.
Athletic Bilbao's Carlos Gurpegi in action against AZ Alkmaar's Vincent Janssen