Many Eredivisie stars have struggled to succeed in the Premier League.
The rumours came after Tottenham Hotspur boss Mauricio Pochettino was spotted attending the international fixture between the Republic of Ireland and Holland.
It immediately led to speculation that he was keeping tabs on Southampton striker Shane Long but it was then reported by Sky Sports that it was in fact Janssen who was the target for Pochettino’s wandering eyes.
Now Spurs have been handed a boost if they are indeed interested in signing the player, as AZ appear to have signed a potential replacement.
The Eredivisie striker has scored 27 goals in the league in the 2015-16 season and scored on his international debut for Holland against England recently.
But should Spurs be careful about signing a player with a fine record in the Eredivisie?
Several players have done well with such a switch – Ruud van Nistelrooy, Graziano Pelle and Luis Suarez for example.
However, others have failed.
Chelsea's Mateja Kezman celebrates his goal
Mateja Kezman arrived at Chelsea on the back of incredible statistics with PSV Eindhoven. He scored 31, 20, 40 and 28 goals in his four respective seasons with the Dutch side but only managed seven for Chelsea before being moved on.
Afonso Alves was another. The Brazilian had scored 48 goals in 48 games for Heerenveen before joining Middlesbrough. His 13 goals in 47 appearances was hardly inspiring.
Jozy Altidore is another example. After scoring 51 goals in 93 appearances for AZ he joined Sunderland, but scored just three times in 52 games.
Then of course there is last season’s Eredivisie top-scorer Memphis Depay, who has certainly not had the impact many expected at Manchester United.
It is not just in England where prolific Dutch league scorers have gone on to struggle. Iceland international Alfred Finnbogason has struggled since leaving sc Heerenveen as did Nikos Machlas at Sevilla. Luuk de Jong flopped in Germany and then at Newcastle United – although has found his feet again back in Dutch football.
Janssen looks like a potential star but the defending in the Eredivisie is certainly not up to Premier League standards and Tottenham are right to be keeping tabs on the player before rushing into any transfer business.