The Crusaders remain on top, four points ahead of the Blues, who took out the Hurricanes 27-17 on Saturday. The Highlanders lifted themselves from the bottom of the table to third place on nine points. The Chiefs are in fourth place on eight points while the Hurricanes are still in final contention on five points.
Robertson congratulated the Highlanders. Events during the week that saw six of their players stood down for breaking team protocols had a galvanising effect for them.
Highlanders coach Tony Brown and his coaching team had a good game plan, and Robertson said he admired what they achieved.
"We were up for the game. We had an understanding that we wanted to put in a real proud performance but they did it to us."
Analysing the effort, he said they made 22 errors, 15 handling errors, they had turned the ball over at the breakdown in the face of the Highlanders' urgency, and showed desperation that had been exceptional.
The Crusaders' set-piece was not their usual force, and while they had planned for it, the Highlanders had executed their plan while the home team had been unable to counter, he said.
Robertson wasn't surprised by the Highlanders' reaction to their upset week. They were a proud organisation with some great players who hadn't been far away in their losses.
"The last time we played them was a game of small margins and they won those, they won those 50-50 balls, we couldn't hang onto the ball on the wing there a couple of times, made a couple of poor defensive reads, they hit the ground off a great kicking structure. We previewed it but they executed it," he said.
First five-eighths Mitch Hunt and flanker Billy Harmon, both former Crusaders, were among the best performers for the Highlanders. Robertson said they were players the Crusaders hadn't wanted to lose but were victims of the contract structure model.
"If we could have kept them we would have, he [Harmon] was exceptional, he's a great player and I'm stoked for him. They've performed like we know they can and they have done for us over the years and well done to them," he said.
Robertson said the Crusaders prided themselves on not having to have a loss to fire them up, but it was a different feeling after the loss.
"The boys are hurting," he said.
The Crusaders were unable to get early flow in the game, and Highlanders captain and hooker Ash Dixon had been in the referee's ear a lot, and they had slowed the game down a lot, especially after the Crusaders had attacked for a long time.
They got their breath back and didn't allow the Crusaders to put constant pressure on them in little moments.
He cited a break by fullback Will Jordan early in the game down the sideline that finished with an error, and instead of giving them momentum, it continued to happen during the game. The accuracy was lacking.
"They defended well on the edge, a couple of last passes were behind guys who were too flat, so it's all those little things that we are normally pretty good at, and we will be next week," he said.