The two-year term is slightly unusual for a 26-year-old marquee player, and means there will be more discussions about Johnson's next contract towards the end of the 2018 season.
The term probably indicates some latent uncertainty from both parties. Johnson wants to be sure that the Warriors are on the right trajectory, after a five-year roller-coaster, on and off the field, involving numerous coaching changes and an endless array of new faces among the playing roster.
Meanwhile, the club needs to know Johnson can shrug off the inconsistency that has plagued his game.
He's a good player, an extremely good player, but has yet to become an NRL great. He's still prone to fading out of matches at crucial times, and his game management has been under the spotlight for the last few seasons.
Now - with a hefty contract tucked away - Johnson needs to go to the next level.
He's never going to be the same kind of organiser as a Johnathan Thurston, Cooper Cronk or Mitchell Pearce but needs to achieve the same level of consistency.
Johnson should become the type of player that is talked about less, as his week to week excellence is taken for granted, just like the above mentioned trio.
The first test comes today. Johnson was the match winner the last time these two teams met, in a 12-10 victory at Mt Smart in June last year. It was one of the better performances of 2016 from the Auckland club, as they stayed in the grind against the Sydney club, before the wheels came off later in the season.
The Warriors have gleaned some positives from the last two performances against the Raiders and the Storm, but how much have those narrow defeats taken out of them?
The Roosters on the other hand have momentum, after their golden point win over the Dragons, and have already banked six wins this season, including impressive victories over the Panthers and Bulldogs.
"We are backing ourselves," said Warriors hooker Issac Luke.
"We know how good the Roosters are but our boys are going well, too. We know what level we need to go too."
