Diana Taurasi scored 23 points, including the go-ahead runner in the final minute, and the Phoenix Mercury beat the Sparks 74-69 on Sunday night to spoil the Sparks' home opener.
Taurasi added six rebounds, six assists and three steals as the Mercury (2-0) outscored the Sparks (1-1) 9-2 over the final 46 seconds for the come-from-behind victory.
DeWanna Bonner had 16 points and 11 rebounds, and Brittney Griner finished with 13 points and 10 rebounds for Phoenix.
Candace Parker had 23 points and 11 rebounds, and Alana Beard scored 16 points for Los Angeles.
A group led by Johnson and Los Angeles Dodgers controlling owner Mark Walter purchased the Sparks after the former owners suddenly relinquished control of the franchise.
Johnson immediately put his stamp on the organization, with the famous "Showtime" moniker from his Lakers days figuring prominently in the Sparks' intro video and the word "Magic" adorning team employees' shirts.
The Sparks fell into a 16-6 hole early in the first quarter but staged a furious rally to take a 30-29 lead at halftime. Parker scored 10 points in the second quarter alone to lead the surge.
The lead changed hands 11 times in a back-and-forth third quarter, and the Mercury emerged with a 51-50 edge heading into the fourth.
The back-and-forth continued deep into the fourth quarter, when Griner's follow shot and free throw gave the Mercury a 68-67 lead with 46 seconds remaining. Parker drained a pair of free throws to put the Sparks back in the lead, but Taurasi made her one-handed runner along the baseline to make it 70-69 with 32 seconds left. The former UConn standout extended it to 72-69 with a pair of free throws.