The 31-year-old captain has called time on his decorated career in Canberra, giving the Brumbies extra motivation as they play-off for the Super Rugby crown.

Lealiifano's news comes after David Pocock, Henry Speight, Sam Carter and Rory Arnold announced they would be leaving the Brumbies at the end of the season.

The team has won seven games in a row at Canberra Stadium, where they will host the Durban Sharks in a knockout clash on Saturday night. The Brumbies will be forced to farewell the departing quintet if they lose to the South African side.

But Lealiifano isn't ready to say goodbye just yet.

"You never know when a good time to step away is," Lealiifano said.

"You want to finish on top and we're in a really nice position at the moment to do that.

"There's exciting times ahead with the quarter-final at home this week and then hopefully continuing on in the competition. It would be really fitting to go out on a high note."

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Lealiifano has been mulling over his future playing career for most of the season. The Brumbies offered him a contract extension but he also had interest from France, Ireland and Japan. Lealiifano decided it was the "right time" to move forward and the offer to join the NTT Communications was too good to pass.

"It's the biggest decision that I've made in my rugby career to farewell my beloved Brumbies," Lealiifano said.

"Playing at Canberra Stadium is something that I'll cherish forever. Putting on that Brumbies jersey is something that I'm really proud of and I'll hold the club close to my heart for a long, long time.

"Hopefully by the end of all this I'm holding a trophy and having a few beers."

The Brumbies squad were "shattered" to be losing another good friend and teammate. While it's been an emotional start to their finals campaign, coach Dan McKellar said they'll approach their quarter-final no differently.

"We'll approach this week like we have all year, nothing will be too different there," McKellar said.

"Obviously there's buzz and excitement about playing finals and we're keen to play in front of a good crowd. We'll keep the emotion in check and be ready to go on Saturday night."

The Brumbies will use their home match as a farewell for the departing players, hoping they can send them out on a high by qualifying for the semi-finals.

Speight will be hoping to return from an ankle injury, while Pocock has been ruled out for the rest of the season.

"You can't hide away and I think it's a motivation," McKellar said.

"When you've got that confidence, self belief and momentum, good things can happen.

"There's genuine motivation there to enjoy the [finals], have some special moments in the dressing sheds, and create our own little bit of history.

"We've got to keep working hard and make sure we set these departing boys and Christian away on the highest possible note."

There's no doubt that Lealiifano is going to be a loss for the Brumbies, but McKellar believes there's plenty of emerging players ready to step up and fill the void.

"We've got a group in the background of emerging leaders we are working with and we're in a good place," McKellar said.

"Lachlan McCaffrey, Allan Alaalatoa, Scott Sio and Joe Powell are all genuine leaders.

"There's plenty of guys who are ready to step up and take over as Christian had to do in the past."

Lealiifano has played 148 games for the Brumbies since making his Super Rugby debut in 2008. He's also captained the side 46 times, with only George Gregan (47) and Ben Mowen (51) ahead of him.

"We're grateful for what he's brought to this club and he'll be a legend," McKellar said.

"He's fearless and his development as a leader over the past few years has been huge. We talk about Larkham, Gregan, and Roff, Christian is right up there."

SUPER RUGBY QUARTER-FINAL

Saturday: ACT Brumbies v Durban Sharks at Canberra Stadium, 8.05pm. Tickets available from Ticketek.