It's a stretch to call the Seattle-Phoenix series a rivalry these days, considering the Storm has a 10-1 record against the Mercury the past two years.

And yet, that's how Swin Cash described the series that renews at 7 p.m. Thursday at KeyArena. The teams clash in the best-of-three WNBA Western Conference semifinals.

"Both of these teams get up to play each other," Cash said. "Since I've been here the last four years, Phoenix has been the team to beat before we won the championship."

Seattle (2010) and Phoenix (2007 and '09) have combined to win three of the past four WNBA titles.

"They've been an awesome team for the last five, six years," Cash said. "We just really enjoy playing them, and I'm sure they say the same about us."

Maybe not.

The defending champion Storm was 7-0 against Phoenix last year, including a two-game sweep in the Western Conference Finals.

This season, Seattle went 3-1 versus the Mercury, including an 85-70 win Friday.

"You can toss out a lot of clichés, but the fact of the matter is we probably know each other better than any other teams in the league," Storm guard Sue Bird said. "For two teams that are supposed to be rivals, we're very close off the court."

In a 12-team league it's not uncommon for friendships to form among competitors, and the Storm and Mercury are connected in many ways.

The close ties begin with the trio of Bird, Cash and Phoenix star Diana Taurasi, who were teammates for two seasons at the University of Connecticut. They led the Huskies to a 71-3 record and a 2002 NCAA title.

The WNBA's two best Australian players — Seattle's Lauren Jackson and Phoenix's Penny Taylor — have teamed in international competitions, including the past three Summer Olympics.

Four Storm players spent time with the Mercury, including Ashley Robinson, Le'coe Willingham, Belinda Snell and Allie Quigley.

Even Storm coach Brian Agler has inside knowledge. He was a Mercury assistant in 2004, when the team drafted Taurasi.

"She's a competitor with a personality," Agler said. "We've got multiple competitors on our team, too, that don't have quite that personality. They have their own personality, but Diana will communicate with you verbally and with body language."

Taurasi, the WNBA scoring champion, is just one of many story lines in the series.

The Storm hopes to become the league's first repeat champion since the Los Angeles Sparks in 2001 and '02.

Jackson (left hip) and Taylor (back spasms) return but are battling injuries that forced them to miss the regular-season finale.

And Seattle enters the series on a roll, winning eight of its past nine games. Phoenix has lost two straight.

"I wouldn't be surprised by anything that happens in this series," Cash said.

Percy Allen: 206-464-2278 or pallen@seattletimes.com