Phoenix's Skylar Diggins-Smith is averaging 14.6 points per game in the playoffs. (Christian Petersen/Getty Images)

The stage is set and two teams remain as the Chicago Sky and Phoenix Mercury tip off a best-of-five series Sunday for a WNBA championship.

The Mercury advanced to their fourth WNBA Finals after defeating the second-seeded Las Vegas Aces in a thrilling five-game semifinal series. They got there by taking out the New York Liberty and Seattle Storm in first- and second-round single-elimination games. The last time the Mercury were in the Finals in 2014, they swept the Sky to earn their third WNBA title.

Phoenix won all three meetings between the two teams during the regular season, with two of the games decided by single possessions.

Despite depleted depth with injuries to Kia Nurse and Sophie Cunningham, the Mercury’s core of Olympians has found a way. Brittney Griner has led the way with 21 points and 9.7 rebounds per game in the playoffs, while Diana Taurasi has averaged 19.7 points per game and engineered multiple late-game comebacks.

The Sky, meanwhile, are playing their best basketball of the season at the right time. After finishing the regular season in sixth place with a 16-16 record, Chicago flipped a switch in the playoffs, defeating the Dallas Wings and Minnesota Lynx in the single-elimination rounds before upsetting the top-ranked Connecticut Sun 3-1 in the semifinals.

Chicago has not been to the WNBA Finals since that 2014 meeting with Phoenix. Allie Quigley and Courtney Vandersloot, who form the longest-tenured backcourt in the league, were a part of that team seven years ago. The Sky will lean on their chemistry, the championship experience of Candace Parker and the firepower of Kahleah Copper, who’s averaging a team-high 18.2 points per game in the playoffs.

What will it take for the Sky to earn their first-ever WNBA championship, or for Phoenix to win their fourth? We break down the Finals matchup, with keys for each team and a championship prediction.

Candace Parker (Kena Krutsinger/NBAE via Getty Images)

Keys for the Chicago Sky

Energy and toughness

It takes a certain amount of grit to finish .500 in an up-and-down season and take your play to another level in the playoffs. The Sky have been the toughest team on the court throughout the postseason, no matter which opponent they’ve faced. They feed off of the energy of Copper, who will need to continue to be the most consistent player on the roster for Chicago to win a title.

The Sky will have success if they take advantage of their depth in this series. As a team that thrives on an up-tempo style of play, they need to run at the Mercury and expose their tired legs in the open court.

Rebound the basketball

This has been a major key for Chicago all season long. The Sky have been able to control the glass during the playoffs with a plus-two rebound margin against their opponents. Out-rebounding the Mercury will be no easy task with the 6-foot-9 Griner in the paint, but the Sky’s communication and rotations will need to be on point for them to limit Phoenix’s second-chance opportunities and create looks for themselves.

Offensive versatility

The Sky have five players who average double-figure scoring. Vandersloot, their lead facilitator, has been brilliant at finding her teammates in the situations where they are most successful. And as a team, the Sky are averaging 20.7 assists per game.

With steady and consistent performances from Parker, Copper and Vandersloot, Chicago can force the Mercury to pick their poison every night in terms of defensive schemes.

Limit turnover numbers

At this point, possession is an automatic key for any Sky game. So far in the playoffs, they haven’t let turnovers affect the outcomes of games as much as they did during the regular season, especially against the Sun, but a trend that plagued them earlier in the year could return. The last two semifinal games, in particular, got a bit sloppy for both teams.

Chicago plays fast and makes quick decisions, so some turnovers can be expected. But in order to win three more games and bring a championship back to Chicago, the Sky will need to limit their unforced turnovers and value every possession.

Diana Taurasi (Jeff Bottari/NBAE via Getty Images)

Keys for the Phoenix Mercury

Others need to step up

Phoenix’s depth has been a reason for concern all season, but it’s reached a new level with Nurse out for the Finals with a torn ACL and Cunningham trying to work her way back from a calf injury. Coach Sandy Brondello said Friday night that the team expects Cunningham to return for Game 2 on Wednesday.

In their absence, the Mercury know what they’ll get from the “Big 3” of Taurasi, Griner and Skylar Diggins-Smith. They’ll need Brianna Turner and Shey Peddy to continue to elevate their offensive production and defensive contributions to sustain Chicago’s depth.

Establish Griner immediately

Griner is playing the best basketball of her career at this moment. The Sky have length, versatility and size inside, but none of their post players can match up one-for-one with Griner. Running their offense through her so she can assert her dominance in the paint early on is as important as anything else. Where Griner goes, this Mercury team goes, and their hopes of winning a title depend on her playing the way she has been.

A fast start

Phoenix needs to apply immediate pressure to Chicago in this series. If the Mercury go down two games at home, I don’t see them being able to rebound on the road and win a championship. It’s critical they secure at least one win on Sunday or Wednesday to give themselves a shot.

Diana Taurasi

The X-factor in this fairytale rematch is Taurasi, the 2014 Finals MVP. The 39-year-old has continued to remind everyone why she’s in consideration for the title of the WNBA’s greatest player of all time. Taurasi has led the Mercury to all three of their championships in 2007, 2009 and 2014. She scored a playoff career-high 37 points in Game 2 of the semifinals and led Phoenix’s comeback in Game 5 on Friday night with 14 points in the fourth quarter.

Taurasi in a WNBA Final is something special, and Phoenix has always relied on her to be at her best in these moments.

Prediction

Chicago Sky 3-2

This series is going to be a battle. As remarkable as the Mercury have been with very little margin for error, I think their lack of depth will catch up to them and be the difference in the series, giving the Sky their first championship in franchise history.

Rachel Galligan is a basketball analyst at Just Women’s Sports. A former professional basketball player and collegiate coach, she also contributes to Winsidr. Follow Rachel on Twitter @RachGall.