WNBA Player Props & Best Bets Today for September 21: Mercury Rising

Tom Oldfield breaks down his favorite WNBA player props ahead of Sunday's two-game playoff slate, including Courtney Williams, and Alyssa Thomas.

Tom Oldfield - Contributor at Covers.com
Tom Oldfield • Betting Analyst
Sep 21, 2025 • 10:03 ET • 4 min read
Phoenix Mercury forward Alyssa Thomas (25) celebrates.
Photo By - Imagn Images. Phoenix Mercury forward Alyssa Thomas (25) celebrates.

The WNBA semifinals are here, and the Minnesota Lynx and Las Vegas Aces start with homecourt advantage as these best-of-five series tip off today.

But the Lynx will have their hands full against a Phoenix Mercury team that just dumped out the defending champs, while the Aces can’t take anything for granted against the injury-hit Indiana Fever, who upset the Atlanta Dream this week. 

The WNBA props market is the place to be for the September 21 hoops action, and my favorite WNBA picks include a feel-good story and a do-it-all veteran.

WNBA player prop bets for September 21

  • Sparks Odyssey Sims Over 3.5 assists (+100)
  • Sparks Courtney Williams Under 13.5 points (-130)
  • Sparks Alyssa Thomas Over 17.5 rebounds + assists (-112)

Odyssey Sims Over 3.5 assists 

(+100 at bet365)

There’s just no quit in this Indiana Fever squad, and their shock Game 3 victory over the Dream took a total team effort. That includes Odyssey Sims, who only joined the Fever in August after injuries to Sophie Cunningham, Aari McDonald, and Sydney Colson left Indiana desperate for help.

Sims had some erratic outings during the regular season, but she stepped up in Thursday’s decider in Atlanta with 16 points and eight assists, and I’m backing her playmaking to be a factor today in Game 1 against the Las Vegas Aces.

The veteran point guard has dished 4+ dimes in six of her past 10 outings, and her ability to get into the paint will be vital here to disrupt a Las Vegas defense anchored by A’ja Wilson, the now four-time MVP.

Sims finished with four assists against the Aces earlier this season while playing for the Los Angeles Sparks, and I see her at least matching that haul today, especially with the potential for 30+ minutes on the court.

  • Time: 3:00 p.m. ET
  • Where to watch: ESPN

Courtney Williams Under 13.5 points

(-130 at bet365)

The Minnesota Lynx had to dig deep to get past the Golden State Valkyries in Game 2 this week, but even a clutch late jump shot couldn’t paper over a tough stretch for Courtney Williams.

While Napheesa Collier and Kayla McBride have been carrying the Minnesota offense, Williams has shot 14-for-43 from the field across her last four contests. She’s fallen short of this O/U number in each of those outings, while making just one of her nine 3-pointers.

Williams can heat up in a flash, but I prefer to fade her points prop in today’s showdown with a Phoenix Mercury team that held the New York Liberty to 73 points in Friday’s Game 3 victory. She also nailed this Under in three of her four matchups against Phoenix during the regular season.

With fewer openings for Williams’ quick-twitch game in the playoffs, she looked a little hesitant against Golden State, and I see her taking a backseat again here.

  • Time: 5:00 p.m. ET
  • Where to watch: ESPN

Alyssa Thomas Over 18.5 rebounds + assists

(-108 at FanDuel)

It was Alyssa Thomas’ Game 3 triple-double that guided the Phoenix Mercury into the semifinals, and now an even bigger test awaits against the Minnesota Lynx. But Thomas has been a reliable stat-stuffer year after year, and I’m taking the Over on this rebounds + assists combo prop in the series opener.

Her season averages of 8.8 RPG and 9.2 APG are already in the ballpark of this pick, and after logging 37 minutes in Game 3 against New York, she’s not likely to get many breathers in this series either.

Thomas has hit this Over in five of her past eight contests, including her 20-11-11 line on Friday, and she’s finished with 9+ assists in six of her last nine games.

The Mercury have a fighting chance in this series if Thomas, Kahleah Copper, and Satou Sabally all bring their A-game, but it all starts with Phoenix’s veteran forward putting her fingerprints all over today’s opening battle.

  • Time: 5:00 p.m. ET
  • Where to watch: ESPN

Today’s WNBA games

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Tom Oldfield - Covers
Betting Analyst

Tom Oldfield’s sports writing journey over the past 20 years has taken him from the Premier League and Champions League to the NFL, NBA, WNBA and MLB, with a wide range of articles and betting previews. Tom has worked closely with London’s Sportsbeat sports news agency as well as (thrillingly!) covering the Toronto Raptors’ 2019 NBA championship run, and he has appeared on BBC World Service and The Back Page podcast.

A graduate of the University of Nottingham in the UK, he is the author of biographies on Cristiano Ronaldo, Rafael Nadal, Gary Neville and Cesc Fabregas, and he co-authors a long-running series of children’s soccer books with his brother, Matt.

As a regular bettor across the top sports leagues, particularly with FanDuel and bet365, he is well versed on all the major markets and the next big game is rarely far from his thoughts. The best betting advice he has received is to monitor multiple sportsbooks to grab the best possible value.

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