Tupaea went down clutching her shoulder midway through the third quarter in Canberra's 84-71 loss to the Townsville Fire at Townsville Stadium on Sunday night.

It is a cruel blow for the 23-year-old who was beginning to show glimpses of her best after a move to Canberra reignited her injury-riddled career.

Tupaea was tangled up with Fire star Lauren Nicholson before the pair hit the deck, with the Capital grimacing as she grabbed her left arm - just beneath the shoulder she injured during a pre-season game.

A second quarter blitz saw Townsville rattle the reigning champions and turn a four-point lead into a 17-point advantage at half-time.

MORE SPORT

Nicholson (25 points) and Shyla Heal (27) were nearly unstoppable against a Canberra outfit being dominated on the boards, with the Capitals looking a shadow of the team that had surged to the top of the standings.

Maddison Rocci led the way for Canberra with 19 points, while Mikaela Ruef (nine points, 12 rebounds) and Kelsey Griffin (10 and 7) finished just shy of double doubles.

The Capitals now have just two games up their sleeve before the finals series tips off, with coach Paul Goriss desperate to sew up a top two finish.

The WNBL finals series has been revamped for the condensed season, with major and minor semi-finals replacing the best of three format.

The top two teams will meet in the first semi-final, with the winner advancing straight to the decider and the loser getting a second chance.

Yet Goriss is refusing to look too far ahead with the Capitals facing a stern test to close out the season.

"You're still living day to day, work to the next game and then work to the game after that. It just seems such a long time ago we were in Mackay," Goriss said.

"It has come around quick but the focus is still on our main goal of winning a championship. We're just getting our preparation done as much as possible.

"We've got to prepare ourselves for each opponent and can't get too far ahead of ourselves. Perth are up and about, and we've got Southside.

"If we want to be top two, we've got to take care of the next opponents and not get too far ahead of ourselves."

AT A GLANCE

WNBL round four: TOWNSVILLE FIRE 84 (Shyla Heal 27, Lauren Nicholson 25, Nadeen Payne 11) bt CANBERRA CAPITALS 71 (Maddison Rocci 19, Kelsey Griffin 10, Mikaela Ruef 9) at Townsville Stadium.