Sydney - The Waratahs will not make the Super Rugby playoffs for the first time in three years if they play the way they did against the Brumbies again, Berrick Barnes says.

GALLERY: Past weekend in pictures

The flyhalf said there was no excuse for the side's failure to score a try in their most important game of the season to date against the Australian conference leaders on Saturday. The loss allowed the Brumbies to pull ahead on the conference table and leaves the Waratahs little room for error in their remaining six games.

Asked whether he thought the Waratahs could still make the finals, Barnes said: ''Not the way we are going at the moment.

''We have got to improve and that's just an honest assessment, the Brumbies far outclassed us. We have two of our hardest games of the season [next], or three in a row. We've got the Bulls and then the Stormers away.''

Barnes's performance on Saturday was the Waratahs' season writ large. Much improved after a slow start to the year but marred by slips that made the difference.

Waratahs coach Michael Foley singled out his playmaker for praise after the match, in which Barnes's direct attacking runs repeatedly got the side on the front foot. But he was also part of the defensive brain explosion in the dying seconds of the first half that allowed the Brumbies to gather momentum on the scoreboard. And he was guilty of knocking on a pass out of a scrum from his halfback Brendan McKibbin, and in so doing butchering one of the Waratahs' two real attacking opportunities in the second half, when the Brumbies were two converted tries ahead.

''I wanted to take the ball to the line and play a bit more, and at times especially in the second half, I overdid it,'' he said. ''There wasn't enough support around me and it got turned over a couple of times, which hurt us. I have to keep trying to do that, I suppose, and balance it up with a bit more kicking. I probably didn't stick to the game plan as I should [have] and I've got to wear that and try to improve next week.''

Barnes was typically honest about his performance - ''You make nine of 10 of those tackles and then you miss one, it shits you, that hurt us'' - but was also searching for answers.

''I wish I had some bloody magic potion to fix what's going on, it's not through lack of effort. I know the boys are trying and we are trying to put a game plan [together], and we spent a lot of time trying to fix it during the week. But … I think we are letting ourselves down with silly errors at certain times, and lapses.''

He also acknowledged the impact a pre- and early season disrupted by injury continues to have on the back line, which has been a turnstile through which almost every back has cycled.

''That's hurting us,'' Barnes said. ''I'll be honest, we've been struggling to be able to get a [connection], losing Drew [Mitchell] and Lachie [Turner] at the start of the year hasn't helped … but we've got to keep plugging away, keep working at it, hopefully we can get a combination going that will start working [because] obviously we were a bit disjointed on Saturday.''