Diana Taurasi scored 21 points, including three 3-pointers in the fourth quarter, to lead the Phoenix Mercury to a 91-76 victory over the Tulsa Shock on Thursday night.
Marie Ferdinand-Harris added 14 points, DeWanna Bonner had 11 points and 10 rebounds, and Candice Dupree scored 13 as Phoenix (19-13) won for the fourth time in five games and clinched at least the No. 3 seed in the Western Conference.
The victory also set up a first-round matchup against defending champion Seattle, with home-court for the series still to be decided. The Mercury and Storm are tied for second place with two games remaining and meet in Seattle on Friday.
"We will just treat it like every other game, we will play the same way we have been all year," Taurasi said. "If you have to change things for a big game, than you aren't preparing the right way. So we will go to the airport early and go to Seattle and see what we can do."
The regular season ends Sunday and the playoffs start Sept. 15. The Storm beat the Mercury 2-0 in the conference finals last year.
Liz Cambage had 22 points and five rebounds to lead Tulsa (3-29), which has lost four in a row. Tiffany Jackson had 15 points and 10 rebounds and Andrea Riley added 14 points and five assists.
Neither team scored for the first 3½ minutes of the fourth quarter until Taurasi hit a 3.
"At the beginning of the fourth both teams were stuck, there were great defensive possessions left and right," said Taurasi, who finished with five 3s. "I think it was a hard game, they are a tough team because they play some weird line-ups and they switch everything, so they make it tough."
Cambage's jumper pulled Tulsa to 73-64 with 6:05 left, but Taurasi hit another 3 just 8 seconds later to push the lead to 12 and the Shock never got closer.
Dupree also had three rebounds to become the 19th player in WNBA history to have 3,000 points and 1,500 rebounds in her career.
The Mercury's reserves — led by Ferdinand-Harris — totaled 37 points on 17-for-32 shooting, the fourth-most points the backups have scored this season.
"Our bench really came through tonight," Phoenix coach Corey Gaines said. "We wanted to use them a little bit more, and they really came through. The key for the game tomorrow are a turnover, that's it. Don't get big turnovers where the other team can score easy."
The Mercury played without second-leading scorer Penny Taylor, who averages 16.7 points a game, who sat out her third game with back spasms. She missed two games before returning on Sunday to play 15 minutes against Los Angeles.
Ferdinand-Harris scored 10 points in the first quarter, making all four of her shots and two free throws, as Phoenix grabbed a 29-24 lead.
Phoenix shot 59 percent from the field in the first half but Tulsa took 10 more shots and trailed 48-45 at the break.
"I thought we executed quite well," Shock coach Teresa Edwards said. "I thought we played well, especially against a team like this. I don't want to be too presumptuous and say we set the pace, but having Phoenix play a half-court game is an advantage for us because they like to run and like to get out. They're a high scoring team and that's how they do, so I thought we did a great job in that first half."
Taurasi hit a 3 and converted a three-point play to help Phoenix get out to a 62-50 lead halfway through the third quarter. The Mercury led 70-62 going into the final period.