The ACT Brumbies were left ruing a costly yellow card as the rampaging Blues surged to a 41-15 win in their Super 12 clash at Eden Park, Auckland.

The Brumbies held the unbeaten Blues at 3-3 until the 20th minute of the first half, when No.8 Scott Fava was yellow-carded for his role in an innocuous scuffle with Blues skipper Xavier Rush.

Referee Andre Watson said he saw Fava throw three punches but didn't witness Rush's involvement, with the Blues No.8 escaping any punishment.

It highlighted a frustrating night for the Brumbies, who failed to pressure the Blues because of poor ball control.

Skipper George Gregan showed his anger in the dying minutes when he knocked the ball away with his hand from an offside position two metres from the ACT tryline, with Watson awarding a penalty try.

Before Fava's sinbin the Brumbies matched the classy competition leaders, despite the home side dominating territory and possession in the Auckland rain.

But cracks appeared in their previously strong defence with only 14 men on the field as the Blues raced in two tries.

Speedsters Doug Howlett, Rupeni Caucaunibuca and Joe Rokocoko have been the form back three of the competition, and with playmaking five-eighth Carlos Spencer pulling the strings, they again proved a handful for the Brumbies.

Fullback Howlett got the first try two minutes after Fava's exit when ACT winger Andrew Walker failed to take a kick cleanly in the greasy conditions.

Both sides scrambled to take control of possession, with the Blues coming up with the ball, and in the ensuing play Spencer found Howlett looming out wide.

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