This comes after the Spurs announced in early June power forward LaMarcus Aldridge underwent shoulder surgery in April, which will prevent him from taking part in the league's restart planned for July.
Zeller has bounced around the NBA in recent seasons. San Antonio marks his sixth different organization since September 2017. He's also made stops with the Brooklyn Nets, Milwaukee Bucks, Atlanta Hawks, Memphis Grizzlies and Denver Nuggets over that span.
The 30-year-old UNC product has made a limited impact since the Cleveland Cavaliers selected him with the 17th overall pick in the 2012 draft.
He's averaged 7.0 points and 4.4 rebounds while shooting 50.9 percent from the field across 412 regular-season appearances (166 starts). He's played 25 playoff games during stints with the Bucks and Boston Celtics.
Zeller didn't play during the initial portion of the 2019-20 season, which was halted by the coronavirus pandemic in March, after being released by the Nuggets in October.
The Spurs lacked frontcourt depth with Aldridge unable to help the team in its quest to secure a playoff berth for the 23rd consecutive season. They are four games behind the Memphis Grizzlies heading into the planned eight-game conclusion to the regular season at the Disney World complex in Florida.
Zeller should split time with Jakob Poeltl at center when San Antonio is using a traditional lineup. It figures to lean far more heavily on small-ball lineups, however, with Trey Lyles and Rudy Gay leading the frontcourt in those situations.
The Spurs' backcourt group, led by Dejounte Murray, Bryn Forbes and Derrick White, will also take on more responsibility on the offensive end without Aldridge available. In addition, DeMar DeRozan's offensive usage could rank among the league leaders during the stretch run.
All told, the addition of Zeller likely won't make a major impact but does fill a void with the franchise's record-tying playoff streak in serious jeopardy.