Mercury fire Corey Gaines

PHOENIX -- The Phoenix Mercury fired coach and general manager Corey Gaines on Thursday after a five-year run that included a WNBA title but a disappointing 2013 season.

Former University of Arizona coach Russ Pennell will serve as interim coach and president and CEO Amber Cox will be interim GM.

Phoenix went into this season with high expectations after adding No. 1 overall draft pick Brittney Griner to a roster that featured star players Diana Taurasi, Penny Taylor and Candice Dupree.

Phoenix won eight of nine games after a slow start to the season, but has lost seven of nine to fall 7½ games behind Minnesota in the Western Conference at 10-11.

"What it really came down to is expectations for this team are not being met," Cox said. "Twenty-one games in, 10-11 on the season and that's just not good enough, quite frankly. We feel like we should be in a better spot after 21 games so we felt like it was time to change things up a little bit and make this move midseason while we still have a third of the season left to go."

Gaines was an assistant under Paul Westhead, his former coach at Loyola Marymount, when the Mercury won the 2007 WNBA title and led them to another championship as head coach in 2009.

Phoenix struggled last season, thanks in large part to a slew of injuries, and wound up with the top pick in this year's draft.

They used it on Griner, a 6-foot-8 dunking sensation who dominated college basketball while at Baylor.

So, far, the rookie center hasn't been the overpowering force so many had predicted, plagued by injuries while trying to mesh with the up-tempo Mercury.

Griner leads the league with 3.0 blocked shots per game and is fourth on the team with 13.9 points while averaging 5.9 rebounds. She has missed five games this season and twisted her ankle in the Mercury's last game, Tuesday against Seattle.

DeWanna Bonner also was injured against Seattle and both are list as day to day.

Taurasi, a former league MVP, leads the WNBA with 21.4 points per game, but the Mercury have struggled defensively at times this season.

Gaines added GM duties after the 2011 season and passed Cheryl Miller on Phoenix's all-time wins list last year. He was 90-101 as head coach.

Pennell served as Arizona's interim coach in 2008-09 after Lute Olsen retired and spent four seasons at Grand Canyon University, where he went 72-44.

"To have that opportunity to coach these young women and pursue a championship is something every coach longs for," Pennell said. "When I was contacted by Amber, it was a little bit surreal because I had never really thought about something like that. But I quickly started thinking, 'Why not?'"