San Antonio coach Gregg Popovich has shed some light on Patty Mills' importance to the Spurs, singling out the Australian guard as one of the NBA outfit's key leaders.

Speaking to reporters before the Spurs played the Bucks in Milwaukee on Sunday (AEDT), Popovich was asked about the importance of Mills' leadership in lieu of Kawhi Leonard's trade to Toronto and the departure of long-time stars Tony Parker (free agency) and Manu Ginobili (retirement).

Leadership: Patty Mills (right), alongside DeMar DeRozan, plays an important role for the Spurs. Credit:AP

Leonard's departure was extremely acrimonious, with the team's star player and former NBA Finals MVP featuring in just nine games last season before orchestrating the trade, and Popovich used the question to offer a surprisingly unflattering assessment of Leonard's leadership abilities.

"Kawhi was a great player, but he wasn't a leader or anything," Popovich said. "Manu and Patty were the leaders.