Per the team's official statement, Griner left for personal reasons, and players and coaches "will have no additional comment on the matter."
Griner has appeared in 12 of Phoenix's 13 games. She wasn't available for Friday's 90-80 loss to the Minnesota Lynx.
Per ESPN's Mechelle Voepel, Griner would have to follow the league's medical protocol, including a seven-day quarantine, if she were to return to the bubble. The WNBA regular season runs through Sept. 12, with the start date of the postseason to be determined.
The Mercury's 6-7 record ranks sixth in the WNBA with nine games remaining. The top eight teams in the league, regardless of conference affiliation, will make the postseason.
Griner leads the Mercury in minutes (31.8 per game), scoring (17.7), rebounds (7.5) and blocks (1.8) this season.