Ill players have been given has long as possible to prove they've overcome the ailment before rejoining the squad. The club doesn't want the mystery illness to impact their preparation for Saturday's clash with the Waikato Chiefs.

Kuenzle was given the all clear and returned to training on Monday, while Irae Simone, Darcy Swain and Mack Hansen are expected in the coming days.

It's unknown whether they'll be fit to travel with the rest of the team to Hamilton due to limited preparation time.

The Brumbies' first away game of the season looms as a daunting task against the Chiefs, who lead the competition in points (105), tries (15), tackles (446) and turnovers won (33).

No team in the Australian conference has beaten a New Zealand side so far this season, including the Brumbies one-point loss to the Otago Highlanders.

The undefeated Chiefs ran riot and scored seven tries against the Japanese Sunwolves last week. Defence will be key in overcoming the New Zealand conference leaders, but luckily for the Brumbies, scrumhalf Ryan Lonergan says it's been one of the strongest aspects of their game.

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"It's just been our errors in our clearance and game management that have been leaking points," Lonergan said.

"Overall, our defence has been quite good but it's definitely going to be a big challenge this weekend against the Chiefs with their electric back three and skillful forwards.

"It's going to be a huge challenge for us but I think our defence will be up to it."

The Brumbies are working on tidying their game management and clearances from their end after the Highlanders put pressure on their young playmakers last week.

Otago's Jona Nareki charged down Noah Lolesio's clearing kick after a restart to score moments after the Brumbies extended their lead.

The Chiefs will impose a greater challenge for the young playmakers and Lonergan has backed his teammates to rise to the task.

"We've been focusing on our clearance and game management. It's really up to those positions that the young guys are in," Lonergan said.

"It's a huge challenge for them, especially across the ditch away from home.

"It's our first travel game, so it's a great opportunity for us to go over there and get some points.

"We're fairly young but we all back each other. Dan [McKellar] reiterated that on Monday, just through using our skill.

"If we use our skill and play with confidence then we can beat any team."

SUPER RUGBY ROUND FOUR

Saturday: Waikato Chiefs v ACT Brumbies in Hamilton 5.05pm