Griner shot 8 for 13 from the field one day after news broke of her engagement to Tulsa Shock star Glory Johnson. Griner also had two blocks, increasing her single-season league record to 127.
The Mercury (28-5), who close the regular season at Seattle on Sunday night, matched the wins mark set previously accomplished by Los Angeles in 2000 and 2001, and the Storm in 2010. Phoenix also extended its franchise-record home winning streak to 15 games.
Sparks All-Star Candace Parker did not play after scoring 24 points Friday night against Seattle.
Jantel Lavender led Los Angeles (16-18) with 22 points. The Sparks, third in the Western Conference, can drop to the No. 4 seed if San Antonio beats Chicago on Sunday in its finale.