Tew also said the franchise could not keep making financial losses, and it was not solely about winning on the field to stop the bleeding of red ink off it.
The Highlanders may have come off a resounding 26-10 win over the Waratahs in Invercargill last Friday night but Tew said that the victory could not camouflage what had been a disappointing season.
The franchise is heading for a budgeted loss and will likely, for the sixth straight season, finish the lowest of the five New Zealand sides.
"It has been disappointing and we want to sit down at the end of the season and have a good talk about that.
But there are a couple of games to go to finish the season so it is better to wait to the end of the season," Tew said.
The NZRU has financially underwritten the Highlanders for the next two years.
Tew said the national union had helped with player retention and he did not buy into the argument that more could be done to get players not playing regularly for other sides to come and play for the Highlanders.
Critics argue it is unfair the Highlanders are struggling for talent while other sides have top players sitting on the bench.
"Certainly, we do endeavour to spread the talent as evenly as we can.
"But I don't think there are many players sitting around not playing for other teams.
"We've also had a pretty poor run with injuries this year.
"And we're not exactly counting a huge number of our teams in contention for the finals. So no, I just don't think that rings true."
Tew said the NZRU had given the Highlanders assistance in retaining players.
"We have worked quite hard in giving the side continuity with players.
"A lot of players who had their first year down there last year have returned for another year and they have worked with the same group of players for a couple of years."
The national union helped bring fullback Israel Dagg back to the Highlanders for another season and secured the services of captain Jimmy Cowan and vice-captain Jamie Mackintosh, after they were thinking of moving elsewhere.
Tew said the Highlanders could not continue losing money.
About as much cost as possible had been taken out of the Highlanders budget so it was now about generating revenue.
Getting a winning team would undoubtedly help - "there is no doubt about that" - but it was not just about that.
"We need to get a firm commitment from the region that the franchise is wanted."
The NZRU would be involved in the end of season review, but Tew said the union was not looking at lessening the number of franchises in the country.
"We've always said to have the All Blacks perform and be competitive we want to have five professional teams.
There is no question about that.
And we have always wanted to have a presence in the bottom half of the South Island."
He could not make any predictions on what would come out of the review.
Tew said he had no comment on the incident involving Highlanders assistant coach Peter Russell, saying he was only alerted to the incident by a journalist, and it was a Highlanders matter.
