Brittney Griner's performance had been up-and-down in her WNBA playoff debut. With veteran Diana Taurasi urging her on, the rookie calmly sank the winning basket.

Griner's turnaround jumper with 4.9 seconds left gave the Phoenix Mercury a 78-77 victory over the Los Angeles Sparks on Monday night in the deciding Game 3 of their first-round series.

"It doesn't matter what you do until the end," said Griner, who finished with six points, four rebounds and four fouls. "I wasn't nervous about it. I didn't think twice."

Candice Dupree scored all but two of her 22 points in the first half, Dewanna Bonner added 19, and Taurasi had 18 points and 10 assists while improving to 6-0 in career elimination games with the Mercury.

Phoenix advanced to the Western Conference finals against top-seeded Minnesota. Game 1 is Thursday.

Kristi Toliver led the Sparks with 22 points. WNBA MVP Candace Parker added 18 points, and Nneka Ogwumike had 13 points and 10 rebounds.

The Sparks were eliminated for the second straight year with a one-point loss. A year ago, they lost 80-79 to Minnesota, which swept the conference finals.

"I'm sick of always being on this podium talking after a loss," Parker said. "Clearly, we keep losing by one point at the end of the season so it's something we're doing."

After Parker gave the Sparks just their second lead of the fourth on a layup with 7 seconds to go, Griner responded with the winning basket for the Mercury.

"The minute she caught it and made her motion to shoot I just knew it was going in," Taurasi said. "I've seen her make that shot all year. For her to be up-and-down all series and take that shot just tells you a lot about Brittney and how mentally strong she is. She's willing to do anything for this team to win."

Parker missed a fling from the wing after getting trapped in the right corner as time expired, dashing her hopes of adding her first WNBA championship to her collection of NCAA titles and Olympic gold medals.

"I forced her out of the paint and I thought I contested," Parker said glumly. "She hit a good shot."

Both teams shot poorly in the fourth quarter, when they each went more than 2 minutes without scoring. The Mercury was 5 of 18, and the Sparks were 5 of 17.

"The defense was pretty good and both teams were tired," Phoenix coach Russ Pennell said. "I'm tired from trying to get them not being tired."

Taurasi found Jasmine James down low for a layin that extended the Mercury's lead to 76-73 with 1:15 left. Lindsey Harding got fouled and made both to draw the Sparks within one point.

Bonner missed a 3-pointer and after a timeout, Parker's layup put the Sparks ahead 77-76.

Taurasi then huddled up her teammates and Griner listened intently.

"She has a calming effect," said Griner, who was the second choice behind Taurasi to take her team's last shot. "She told us it's going to be OK, get the stop, get the ball back and we'll be fine."

The Mercury clinched their fifth conference finals appearance and fourth in the last five years.

Phoenix saw most of its seven-point lead evaporate in the third, when Griner picked up her fourth foul and sat the rest of the period. Toliver's jumper beat the buzzer to leave the Sparks trailing 66-64 heading into the fourth.

"We played well in spurts, but didn't play well enough for 40 minutes," Toliver said. "We lost our composure a little bit, turned the ball over, regained it, got stops, got on the boards. It just went back and forth. We just couldn't capitalize on our last possession."

The Sparks came in 0-for-21 from 3-point range in the series, and they finished the game 2 of 16.

The Mercury rallied from eight points down to lead 42-40 at halftime. Griner picked up her third foul and Taurasi got her second in the final 1:30 of the second quarter. Dupree, Taurasi and Bonner combined to score all of the Mercury's 23 points in the second, when they shot 73 percent.