Joseph believes his side has been playing well but says it is not executing enough opportunities.
"The concern for the team is if you go through the statistics of our team, we are the highest line-breaking team in the competition," Joseph said.
"We are fourth or fifth in the lineouts, the same in our attack, and we are the third defensive team in the competition.
"So in terms of how we are playing and how we are doing, we are right on the money. But we are just not getting over the final hurdle."
Joseph said the coaching team had demanded the players dig deep this week, asking them to lift by another 5%.
Errors plagued the side last week in a close loss to the Hurricanes, and Joseph said that came down to individuals making mistakes.
"Guys just have to concentrate more. It is something you have to work on and concentrate and what you find in the team, it is unusual mistakes.
"I have not seen guys drop balls like last week in training but we just have to stick at it. That is sport, I suppose."
With the Highlanders having lost their past two games, sitting just outside the top six, many are suggesting it is turning into a repeat of last year, when the team faltered in the second half of the season.
But Joseph is not buying into that, saying if he listened to the radio and believed everything he read, he would not be coaching.
"I can't think of any time last year when we had four guys come off with season-ending injuries and that was just in the first half [against the Sharks]. We have beaten ourselves a lot of the time.
"The Stormers were a team which beat us. The Brumbies was a game that went down to the wire, and we lost our first five-eighth, out for the season.
"The Sharks game, we lost four players with injuries in the same game. Last year for me, we lost to teams we should have beaten, given our previous results.
"The Stormers are top of the table, the Brumbies are top of their conference, the Hurricanes are right behind us and the Sharks are just in front of us. That just reflects the tightness of the competition."
The Bulls stand at the top of that competition, and have won their past five games.
They were predicted to struggle at the start of the season, after losing a raft of players, but have played simple, solid rugby to defy the critics.
Captain Jamie Mackintosh is welcomed back into the Highlanders after having a rest last week, and Joseph is expecting a big game from his skipper.
Nasi Manu and Adam Thomson did not train much during the week but Joseph said as players were playing on firm grounds and then training on soft grounds, they were picking up leg injuries.
The Highlanders are moving into must-win territory and to stay in finals contention, must beat teams above them. But the Bulls will be tough, and do not let chances go.
The Highlanders, especially inside backs Aaron Smith and Mike Delany, must treat the ball like gold, make the tackles when needed and try to break down the Bulls' structure.
Delany replaces Chris Noakes in the backline, while there is some major reshuffling up front.
Hooker Jason Rutledge gets a start ahead of Andrew Hore, Tim Boys will start at openside flanker, Adam Thomson moves back to blindside and Nick Crosswell moves from No6 to lock.
Josh Bekhuis has been bracketed with Hoani MacDonald on the bench. Wellington flanker Scott Fuglistaller, who has joined the Highlanders as permanent cover for the injured John Hardie, is also among the reserves.
