The Brumbies have won their past four games in a row and can stretch their streak to five if they topple the NSW Waratahs at Parramatta on Saturday night.

A win in Sydney could also clinch the Brumbies' return to the Super Rugby play-offs pending results in other matches, but the team is also trying to break a winning curse dating back to 2007.

The Brumbies haven't won more than four consecutive games since the final season of George Gregan, Stephen Larkham and Jeremy Paul 12 years ago.

But they are set up to make a charge to the finals with two games left in the regular season and can end the Waratahs' faint finals hopes if they win this weekend.

Brumbies coach Dan McKellar has brought a touch of the past to his squad, inviting the recently retired George Smith into the inner sanctum last week while inaugural ACT captain Brett Robinson joined the squad in Argentina.

It has proved the perfect tonic for the players, who have lost just one of the past seven games and are five points clear at the top of the Australian conference.

The Brumbies have scored 97 points and conceded just 19 in the past three games, but attack coach Peter Hewat has warned the squad to brace for war against NSW.

Former Waratahs point-scoring ace Hewat expects NSW to fire when their play-off hopes go on the line in the derby contest.

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"We know it's going to be a big battle this week, the Waratahs have been good defensively all year so it's a big battle to try to break them down," Hewat said.

"It's not going to be the sort of game it was last year where it opened up a bit, it's going to be an old school battle. It's going to be intense. The NSW and ACT games are always physical, this isn't going to be any different. We're desperate and they're desperate."

McKellar will name his team on Thursday, with minimal changes expected to the winning side. Winger Henry Speight is racing the clock to try to overcome a calf problem, but the Fijian flyer could be a late withdrawal from his second last game for the club.

Andy Murihead would come into contention to replace Speight on the right wing, while McKellar was yet to decide if he would continue with a forwards-heavy bench.

Lachlan McCaffrey made his comeback from injury last week and will be pushing for a starting spot, but the back row of Tom Cusack, Jahrome Brown and Pete Samu have given McKellar a selection headache.

The Waratahs have their own selection dramas as coach Daryl Gibson weighs up whether to rest Wallabies stars, while Israel Folau hasn't played since April after a controversial homophobic Instagram post.

Folau was regarded as one of Super Rugby's most dangerous attacking weapons, but the Brumbies managed to contain him in recent clashes and the cross-code star went try-less in his last four games against the ACT side.

"I think they've been actually been more direct [without Folau]," Hewat said.

"You've seen them change that up over the last month or so, using skills in their forwards and they've got Kurtley [Beale] out the back swinging either side. When Kurtley is scheming around, he's dangerous. So we have to defend well, that's big for us. To make sure our defence is in tact and we're well connected."

The Brumbies are on 39 points while the Melbourne Rebels are on 34 points and still in contention for Australia's guaranteed place in the finals. The Waratahs are on 30 points and while it's mathematically possible for them to win the Australian conference, their play-off hopes more likely lie in trying to sneak into the top eight. "I imagine their motivation is that they have to keep winning, like we all do in Australia," Hewat said.

"We're just trying to keep building from week to week. We think we've improved weekly and it's no different this week. We know there will be an edge to it, but we're ready."

SUPER RUGBY ROUND 17

Saturday: NSW Waratahs v ACT Brumbies at Parramatta, 7.45pm.