Janmaat is wary ahead of the game against Louis van Gaal’s team because of how unpredictable he feels the Dutch coach can be.
“Both me and Tim (Krul) have experience of working under him, but he is so adaptable that it is still hard to know what he is going to do,” said Janmaat.
“We really want to win Wednesday’s game, and they have a lot riding on it as well, so it should be a good occasion.”
Janmaat and Krul were both members of the Netherlands World Cup squad to perform under van Gaal in the tournament in Brazil last summer.
Van Gaal has shown himself to be versatile with a number of systems used at Old Trafford this season, some of which have worked and some of which have seen his players struggling to adapt.
Van Gaal has also mixed up the players he uses in his Manchester United side, with younger stars used alongside expensive and more experienced stars.
It all adds together and makes them very difficult for Newcastle to prepare for.
Newcastle have the home advantage and they need to try and use that to their advantage, putting pressure back onto van Gaal’s team and exploiting the weakness which comes with unpredictability.
Achieve that and the Magpies should be a step closer to the top half of the table.