San Antonio assistant coach Ettore Messina served as coach in Game 3 against the Golden State Warriors, a game the Spurs lost 110-97 that put them in a 3-0 series deficit.
Messina was coaching his first NBA playoff game, but he has won more than 10 titles in the Euroleague, Russian SuperLeague and Italian League.
''We are all hurting,'' Spurs veteran Manu Ginobili said after the team's morning shootaround on Thursday.
''We want to be next to Pop, we want to support him, but we've got to go out there and compete today. But, for sure, we are toiling. It's not an easy day to be here.''
The move came a day after Erin Popovich, the wife of longtime Spurs coach Gregg Popovich, died at 67. The Spurs confirmed Erin Popovich's death Wednesday, but did not provide further details.
''We mourn the loss of Erin,'' Spurs general manager RC Buford said in a team statement. ''She was a strong, wonderful, kind, intelligent woman who provided love, support and humor to all of us.''
The Popovichs have two children and two grandchildren. They met at the Air Force Academy in 1970s when he was an assistant coach for the Falcons. Erin's father, Jim Conboy, was Air Force's head athletic trainer.
Gregg Popovich has coached San Antonio since 1996, leading the Spurs to five NBA titles. He ran the Spurs' practice Wednesday.
Messina came to San Antonio from Russia in 2014, where he coached European power CSKA Moscow. He is a two-time Euroleague coach of the year and has also coached in Italy and Spain. He served as a coaching consultant for the Los Angeles Lakers in 2011-12 and now is making the jump to a full-time NBA coach.
The 58-year-old Messina has won four Euroleague championships and coached Spurs veteran Manu Ginobili in Italy in 2001. In recent seasons, his name was raised as a candidate to become the first European coach to become a head coach in the NBA.
Information from The Associated Press was used in this report.