The Highlanders scored a bonus-point win on Saturday night in beating the Blues 27-20 in Auckland, and with it locked up the Gordon Hunter Memorial Trophy for the year.
The win kept the Highlanders handy to the playoff picture, just one point out of the top six.
One of the sides just above them is the Crusaders, the Highlanders' next opponent, in Christchurch this Friday.
Joseph said it was the first of three important games left, and the side needed to be totally accurate for Friday night's game against a perennial contender, which is fresh off a bye.
"If we can put it all together, then we have shown we can match it with the best of the teams.
"But we have to execute well and cut out the mistakes," Joseph said.
"Last year I was screaming out for X-factor players.
"Now, if we can get enough ball, we have the players who can make and score the tries.
"But we have to do those basics well and cut out the silly mistakes."
After the Crusaders game the Highlanders take three weeks off for the June test window, before taking on the Chiefs and Reds to wind up their season.
They have a bye in the final round.
Joseph was happy with the win on Saturday night, although he felt the side could have played better.
"The team itself did not play its best game but they were playing against a very hungry and competitive team which was always going to make it hard for us.
"There were touches of brilliance from the likes of Hosea [Gear] and Tamati [Ellison] and they showed what they can do if we put it all together.
"But for whatever reason, it might be a knock-on or a dropped pass, we just couldn't get any pressure going.
"We can't afford to make those mistakes in the coming weeks."
The Highlanders at least have control of their destiny, although only one of the remaining three games is at home (Chiefs).
They managed to beat the Crusaders away from home last year, in Nelson, but the red and blacks appear to be coming into some ominous form, putting 50 points past the hapless Blues last week.
The Highlanders have a relatively short turnaround this week and will be without their All Blacks until Wednesday.
Joseph said that was not ideal but the side would just have to get on with it.
On the positive side, English flanker James Haskell will be available, after serving a four-week suspension for punching.
There were no injuries from Saturday night, although Gear was a bit sore.
But he should be happy after he was rewarded for his good form of the past couple of weeks and committing to New Zealand rugby for the future, by being called into this week's All Black training squad, which gathered in Wellington yesterday.
"That is good news for Hosea and the team.
"As a team and coaches you want guys to be picked for the All Blacks."
Gear replaces Cory Jane, who has a sprained ankle, while Chiefs hooker Hika Elliot comes into the squad to cover Keven Mealamu, who is still struggling with a calf injury.
