Rodney Stuckey added 20 points off the bench and Greg Monroe had a double-double of 15 and 10 rebounds for the Pistons, who handed Loyer a victory one day after taking over behind the bench for the fired Maurice Cheeks.
The Pistons, who entered the contest one-half game out of an Eastern Conference playoff spot, improved to 22-29 on the season with a third straight win.
The Spurs turned the ball over 19 times en route to their seventh road loss.
Marco Belinelli paced San Antonio with 20 points.
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