Teenage flyhalf Matt Toomua faces a huge challenge when he makes his starting debut for the Brumbies in their key Super 14 clash against the Hurricanes in Wellington on Saturday.

Toomua, 19, was named on Thursday to replace playmaker Christian Lealiifano who tore his hamstring while scoring the match-clinching try against the Bulls last Friday.

The seventh-placed Brumbies are aiming to keep alive their three-match wing streak against the fourth-placed Hurricanes in the quest for a semi-finals berth.

The option of using the steady Gene Fairbacks at five eighth was lost when he was ruled out with a groin injury.

But Brumbies coach Andy Friend backed youngster Toomua to succeed.

"This is his second year as part of the Brumbies squad and he's shown tremendous growth as a player and has proven he is ready for this extra responsibility," Friend said on Thursday.

"He's a player with a strong kicking game and an excellent sense of game control and I know he's very keen to get out there and show what he can do on Saturday night."

The Brumbies backline regains left winger Alfi Mafi from a groin injury, allowing Wallabies captain Stirling Mortlock to revert to the centres outside Tyrone Smith.

However, lock Mark Chisholm (wrist), fullback Mark Gerrard (hamstring) and winger Clyde Rathbone (quadriceps) were among players unavailable.

The suspension of prop Guy Shepherdson opens the door for Selesi Ma'afu to start while Ben Hand's hamstring strain has cleared up and he will take up his place in the second row again next to Peter Kimlin.

Brumbies: Adam Ashley-Cooper, Francis Fainifo, Stirling Mortlock, Tyrone Smith, Alfi Mafi, Matt Toomua, Joshua Holmes, Stephen Hoiles (captain), George Smith, Mitchell Chapman, Peter Kimlin, Ben Hand, Salesi Maafu, Stephen Moore, Ben Alexander. Reserves: Huia Edmonds, Nic Henderson, Henry Vanderglas, Julian Salvi, Patrick Phibbs, James Stannard, Afusipa Taumoepeau.

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