'They were bloody good last time': How Blues plan to prevent Brumbies upset

The Blues have swept virtually all before them in Super Rugby Pacific but are wary of what the Brumbies will bring in Saturday's semi-final after a torrid clash against them last month.

Without a number of rested stars, the Blues needed an injury time drop-goal from Beauden Barrett to fend off the Brumbies 21-19 in Canberra, where the home side slowed down the visitors' quick ball with hard work at the breakdown.

"They were bloody good last time we played them," Blues forwards coach Tom Coventry told New Zealand media on Thursday.

"I know they're pretty confident with the way they played against us so it's a big challenge for us.

"We respect them deeply ... We're going to have to be at our very best. We weren't last time."

The top try-scorers in the competition, the ladder-topping Blues are unlikely to be thrilled with the rain forecast for Eden Park on Saturday which could stifle their attack and play into the Brumbies' hands.

The Brumbies last won at the Auckland stadium in 2013 in a wet game dominated by penalty goals.

The Blues, who hammered the Highlanders 35-6 in the quarter-finals, have rejigged their pack, bringing in Nepo Laulala to replace fellow All Blacks prop Ofa Tuungafasi.

Lock Josh Goodhue has been promoted to the starting 15, while AJ Lam slots into the left wing in place of the injured Bryce Heem.

The Brumbies, who overhauled the Hurricanes at home last week and are the only Australian team in the semis, will look to keep the season alive for departing coach Dan McKellar and a slew of long-serving players.

"It doesn't interest us to know we were the best-performing Australian team," McKellar said.

"We want to be the best team in the comp."

They have been reinforced by loose forward Rob Valetini, who returns as starting number eight after a month out with a hamstring injury.

The winner will meet either the Crusaders or the Chiefs, who play the other semi-final in Christchurch on Friday, a repeat of last year's domestic Super Rugby Aotearoa decider.

Scott Robertson's Crusaders won the New Zealand title with a 24-13 win that day to secure a fifth championship trophy in five years but suffered a rare defeat at the same venue in a re-match in March.

The Crusaders are a different beast in playoffs, however, having never lost one at home in 26 matches.

Robertson, who will be coaching his 100th Crusaders game on Friday, took little heart from his team's finals record.

"Any Kiwi team can effectively have their moments that can change games," he said.

"We've reminded each other from the last (Chiefs) game."