The Brumbies have all but guaranteed their Super Rugby finals spot, capitalising on the Rebels' upset loss to the NSW Waratahs to beat the Sunwolves in Tokyo.

The Brumbies' 42-19 bonus-point win on Saturday takes them to 39 points on the ladder, five clear of Melbourne with two games to play.

Second-year coach Dan McKellar, an unknown when the former ACT forwards' assistant had replaced Stephen Larkham in 2018, has returned the Brumbies to form.

They have been without the best openside flanker in the world David Pocock for most to the season but have still found a way to win.

The Sunwolves are anchored to the bottom of the ladder but have beaten the Waratahs and Chiefs this season and had posed a danger to the Canberra outfit.

The home side scored the first try when the "Tongan Godzilla" Hosea Saumaki broke through in the opening minute but the Brumbies quickly responded.

Wallabies No.8 Pete Samu squared the ledger in the ninth minute before Irae Simone and Tom Banks scored from backline moves inside the half-hour.

Brumbies super-sub Connal McInerney replaced hooker Folau Faingaa at halftime and scored a hat-trick in the second half, all from rolling mauls.

He had never scored a Super Rugby try and becomes the fifth player in Super Rugby history to score three off the bench.

The Brumbies next face the Waratahs at Bankwest Stadium in Sydney before hosting Queensland in the final round.