Assistant coach Ettore Messina filled in for Popovich in the Spurs' 110-97 loss to the Golden State Warriorsthat put San Antonio in a 3-0 hole.
Erin Popovich died early Wednesday at the age of 67. She had been battling an illness for an extended period. The couple was married for four decades and had two children -- Jill and Mickey -- as well as two grandchildren.
"Very sad day," veteran guard Tony Parker said at the team's shootaround Thursday morning. "Very emotional. It's going to be very hard to play basketball today, but we have to do it.
"For me, it's very emotional. She was a great lady, always [considered her] a mom. Everybody knows that because I arrived at 19. It's very, very emotional. ...She was a great lady, very caring, showed a lot of love. She was unbelievable."
Added Manu Ginobili:"You don't know how to handle it. It just happens. We're all devastated. We're hurting. We all know the type of guy Pop is. Not many people know the type of gal that Erin was. It's painful."
Spurs general manager R.C. Buford said he spoke to Popovich on Thursday morning and said the coach was "overwhelmed" by the support and "very appreciative of the love that's been shared" but wanted the team's focus on the game.
"We're all suffering a profound loss to a really important member of our family and our team," Buford said. "Erin and Gregg were best friends who were together for 40 years, and Erin's impact and influence on our organization, on our families, on our players and their families will be felt for years to come. ...
"As you'd expect from Pop, he wants our focus to be about the game today, about this series, and that's what today will be about. We'll miss Erin a lot, and the focus of our team will be on supporting Pop. But we've got basketball to get back to."
Ginobili said the Spurs will "do our best" to focus on basketball, even though their minds are elsewhere.
"As an individual, you try to support, you try to be there. As a team, I guess you show your support and then respect trying to go out there and compete even harder than you ever did. It's what we can do. And we'll try to honor it."
The outpouring of support from across the league continued Thursday.
"Pop might be the most admired man in the NBA, for many reasons, and there is an outpouring of support and grief from everybody around the league, but it hits home especially for those of us who were a part of the Spurs family and who have been so impacted by Pop and Erin over the years," said Warriors coach Steve Kerr, who played under Popovich for the Spurs.
"I knew her well. She was close with my wife when I played here. Erin was sort of the balance that Pop needed. I still remember when he traded me to Portland in 2001. He called me up to tell me the news and he said, 'I don't think I can go home because Erin is going to be so mad at me for trading you.' ... She was part of the family."
Miami Heat star Dwyane Wadesaid he "stopped everything" when he heard the news.
"LeBron [James] said it best: We all compete against each other in this league, [and] we all are on opposite benches, but in some form and some way, it's a bond and a brotherhood in the game of basketball for everybody," Wade said. "So it's a sad moment for the NBA whenever someone loses someone close to them, like Coach Pop did."
Parker said the support has been nice to see.
"It puts everything in perspective that it's way bigger than basketball," Parker said. "So that was very nice to see all these people, the whole NBA, showing love for Pop and for his wife."
Popovich, who has won five NBA titles since becoming coach in 1996, had run the Spurs' practice Wednesday.
Golden State has a 2-0 lead in the best-of-seven series.
"Very tough, very tough in the middle of the playoffs like this," Parker said of the switch from Popovich to Messina for Game 3. "But we're going to try to do our best, give it 100 percent and try to get a win for him and his wife."
Added Ginobili: "Not having him with us, not having him here today, it's hard."
Warriors guard Klay Thompson said the news has been hard for Kerr, Warriors associate head coach Mike Brown and "anyone who's been around Pop for a long part of their career."
Kerr said he texted Popovich on Wednesday but hadn't had the opportunity to speak to him yet.
"We all grieve and at the same time try to celebrate her life and her legacy," Kerr said. "You've got to be special to be married to Pop. She was very kind. ... She kind of kept him in check. She was a wonderful person. Pop has told me a lot over the past few years about how happy they've both been being relatively new grandparents over the past five years or so.
"We all mourn her loss."
ESPN's Michael C. Wright contributed to this report.
Popovich will not coach Game 3 against Warriors
Michael C. Wright reports on the scene in San Antonio as the Spurs prepare to face the Warriors after the death of coach Gregg Popovich's wife, Erin.