"YUCK, poor Robertson clearly the best coach and misses out to Ian Foster of all coaches. What a sham this whole process has been - Razor was no chance and the other 24 invited to apply knew they were no chance too. Id [sic] be gutted if he was coaching the chiefs bt [sic] nz," one fan posted on Twitter.
"I am disappointed (but not surprised) to hear that Ian Foster will be the next All Blacks coach. NZRU are very risk averse which means more of the old guard. Hard luck Scott Robertson you would have been a breath of fresh air," another wrote.
The social media reaction wasn't all bad, though.
Some fans pointed out that although Robertson holds a stunning Super Rugby record, Rugby Union was a different ball game.
Others said Foster at least deserved a chance.
"Well it's confirmed. His assistants well most likely be Plumtree Mooar, Feek, McLeod. Foster deserves an chance. He's not Hanson, [sic] he has his own ideas. And the whole coaching panel has changed," one user posted.
Meanwhile, some in the rugby media world also voiced their opinions on the situation, with Daily Telegraph telegraph journalist Jamie Pandaram saying "rival teams will be relieved" by the All Blacks' appointment.
"Ian Foster named as the new All Blacks head coach for two years (2020-21). Many rival teams will be relieved the Kiwis didn't give the job to Scott Robertson," Pandaram tweeted.
Mike Hytner from The Guardian wrote: "Seen as a risky appointment in some parts, Foster's first task will be to win over a sceptical New Zealand public after the popular Robertson was overlooked."
On the other hand, Routers wrote that Foster could be out the door if he can't keep winning.
"Foster's promotion from assistant under Hansen on a two-year deal is an attempt to extend that dynasty but he knows as well as anyone he will be out the door long before the 2023 World Cup if he cannot keep the All Blacks winning.
"Their inability to break down increasingly efficient defences, coupled with constant shuffling of the midfield selections, was criticised by pundits and is something Foster will need to address before his side meet Wales at Eden Park next July."
Foster didn't shy away from acknowledging the reaction when speaking to media at a press conference in Auckland today.
He said he knew he some work to do in gaining the public's full confidence and support.
"I've got a job now to reinvent myself a bit with the public, with the media," Foster said. "I've been eight years as an assistant coach, my job was to be the best assistant coach that the All Blacks needed me to be.
"Now it's time for you to see me in a new light and that's up to me to show you that I'm innovative, I've got a sense of direction of where I want this team to go and I'm extremely passionate about adding a new touch to it."
In making the announcement, NZR Chairman Brent Impey said Foster had come through as the preferred candidate following a lengthy and robust interview process.
"The NZR Board has today ratified Ian Foster as the new head coach of the All Blacks from 2020. He brings world-class international experience to the role, an incredibly strong coaching team, and we think he'll do an outstanding job.," Impey said.
"The interview process was extensive and really difficult, which reflects the very strong applications from both candidates."
Impey said Foster would be joined by four other coaches, who will be announced in due course.
"While we can't confirm the full make-up of the coaching team today, we're delighted with the quality they bring − they have a wide range of coaching experiences and are a diverse group of thinkers."