The Bulls have ended NSW's record-equalling five-match Super 14 winning streak with a tense 16-13 victory over the Waratahs in Pretoria.

The defeat leaves the Waratahs' season on a knife edge.

Although the three-point loss was good enough for the Tahs to gain a precious bonus point and maintain second place on the competition table with two rounds remaining, their participation in the playoffs is anything but assured.

The Waratahs are still in control of their own destiny and can secure a home semi-final with victories over the fourth-placed Stormers in Cape Town next Saturday and the Queensland Reds in their final game of the regular season in Brisbane.

But a loss in either could yet cost them a semi-finals berth.

The Waratahs were left to rue not clinching a playoff berth with success over the Bulls after dominating the opening 20 minutes at Loftus Versfield.

They were desperately unlucky not to have been leading 14-0, with halfback Luke Burgess having the ball knocked from his grasp when he seemed certain to score the visitors' second try.

NSW were leading 7-0 at the time and who knows how the match would have unfolded had the Waratahs been able to ram home their early advantage with a two-try lead.

Alas, a Morne Steyn field goal seven minutes from time earned the defending champion Bulls only their fourth win of an otherwise disappointing season.

NSW captain Phil Waugh lamented his team's loss of intensity after such a promising opening.

"We started the game pretty well and then we fell away," Waugh said.

"We ended up with 13 points and we dropped the ball over the line next to the posts and that would have taken us to 14, so there's turning points in the game that cost you and we can't afford to do that.

"We prepared well, we didn't run out of legs. We just executed poorly. A couple of turnovers at crucial stages in the game cost us."

The Waratahs had opened the scoring in the ninth minute through a lovely try to teenage centre Rob Horne.

After a probing run from Burgess, barnstorming No.8 Wycliff Palu straightened the attack before putting Horne over in a handy position.

Five-eighth Kurtley Beale's successful conversion made it 7-0.

But Burgess's earlier near-miss proved costly as the Bulls, gradually working their way into the contest, narrowed the gap to a point with a 19th-minute drop goal to Derick Hougaard and Steyn penalty goal on the half hour.

Winger Lote Tuqiri missed with a long-range penalty goal attempt on the stroke of halftime, leaving the Waratahs clinging to a 7-6 lead at the break.

The Bulls hit the front for the first time in the 44th minute when hooker Derick Kuun capitalised on a poor midfield kick from NSW fullback Sam Norton-Knight to score the home side's only try of the match.

Steyn added the extras to nudge the Bulls six points ahead.

In a strange decision, the Waratahs opted for Tuqiri over the more reliable Beale when they received a penalty 42 metres out from the Bulls line.

Tuqiri hooked the ball left before Beale slotted a penalty four minutes later to reduce the Bulls' advantage to 13-10.

Beale then locked the game up when he landed a field goal with quarter of an hour left on the clock, but the Waratahs' reprieve was brief with Steyn landing the killer blow from close range in the 73rd minute.

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