RIVERSIDE, Calif. >> Even a nationally ranked women’s volleyball team can find room for improvement, as Hawaii demonstrated Sunday.

The 19th-ranked Rainbow Wahine earned their ninth consecutive victory by boosting their hitting percentage from their previous match during a 25-19, 25-11, 25-17 sweep of UC Riverside at the Student Recreation Center Arena.

UH (22-3, 12-2) extended its lead in the Big West Conference’s standings to one game over second-place Cal Poly (17-7, 10-2) and two games over UC Santa Barbara (19-4, 9-3) heading into a bye week. The Wahine also remained undefeated in 27 matches against Riverside since the series began in 1974.

In their four-set victory Friday night at UC Davis, the Wahine hit between .152 and .182 in each of the final three sets after compiling a .484 percentage in the first set, and finished at .286. But against the Highlanders (6-18, 2-11), UH forged a season-high .358 percentage, hitting .636 with no attack errors in the second set (14-0-22).

Freshman hitter Hanna Hellvig and senior hitter McKenna Ross each had a match-high 11 kills, Ross hitting a career-high .688 with no errors on 16 attempts. Junior hitter Brooke Van Sickle added nine kills.

In the process, the Wahine showed themselves as still a work in progress.

“Don’t get me wrong, I’m very happy with the win but not too happy with some of the plays,” UH coach Robyn Ah Mow said. “There were some plays where I was thinking, ‘Are we playing volleyball?’ I thought we made a lot more mental errors.”

So how has the team’s concentration been developing this season?

“I think it’s gotten better but in some games, we lose focus,” Ah Mow said. “Some games are just less focused than others. There’s a lot of stuff we’ve got to work on.”

Ah Mow even attributed the improved hitting percentage to “less errors, less mistakes in focus,” she said.

Riverside exploited Hawaii’s early mistakes to keep pace in the first set. The Highlanders scored four of their first five points on UH hitting and serving errors. Both teams tied the score 10 times and exchanged the lead five times.

“They have a really great defense,” Ross said. “They did a great job of not letting the ball hit the floor on our harder hits.”

Ah Mow elaborated.

“They just had some crazy digs, crazy ups,” she said. “They play hard defense.”

But at 16-16, the Wahine made their move: a 6-1 surge that put them ahead, 22-17. Van Sickle pounded two kills during the spree, with freshman middle Amber Igiede adding a kill off senior Norene Iosia’s quick set before joining freshman hitter Riley Wagoner to block the Highlanders’ Alexis Vanlandingham.

Ayla Fresenius enabled Riverside to draw within 22-19 when teaming with Kat Lowry on a block against Hellvig and punching a kill. But, following a timeout, UH scored the next three points.

Iosia’s quick set found Igiede for another kill, then Hellvig and Skyler Williams combined to block Fresenius. Ross ended the set with a cross-court kill from the left pin.

UH dominated Set 2 early by building an 8-1 advantage and only allowed the Highlanders to score consecutive points just once when cutting Hawaii’s 17-7 lead to 17-9.

Hellvig and Van Sickle combined for four of the points, with Van Sickle scoring two service aces after Hellvig hit two kills from the right side. But Set 3 resembled Set 1.

The Wahine turned a 5-2 deficit into a 9-7 lead, with Ross pounding three kills and Williams providing two kills off quick sets and a block assist during the recovery. Yet Riverside regained a 12-10 advantage before UH moved ahead, 15-13.

After Isabella Scarlett’s kill narrowed the Highlanders’ deficit to 15-14, the visitors scored the next five points. Williams registered another kill and another block assist during the 5-0 blitz, and Bailey Choy added her second service ace.

Riverside drew within 20-16 but Van Sickle smashed three kills during the Wahine’s ensuing 5-1 surge. The junior transfer from Oregon converted match point by smashing a cross-court kill from the left antenna.

“They are very good defensively but we knew that, Hellvig said. “We were more prepared. We just had to win serves and pass.”

Iosia had 20 assists and eight digs, and now needs 17 digs to pass Suzanne Eagye and take over ninth place on the program’s career list. Igiede finished with four block assists and Rika Okino had 15 digs, both match highs.

Lowry collected eight kills for Riverside and Morgan Kline had 22 assists and 13 digs.

The Highlanders did not hit above .100 this season against the Wahine, hitting .096 Sunday and .022 at the Stan Sheriff Center on Oct. 18.

The Wahine finish out the regular season at home with matches against Cal State Northridge (12-13, 7-6) on Nov. 21 and Long Beach State (10-15, 7-6) on Nov. 22.