Petkovic, who has played with bone spur problems in his right ankle this season, made 10-of-17 shots from the field and grabbed eight rebounds. It was Minnesota's first win since March 28 at Charlotte.
The Timberwolves' late-season slide has coincided with the absence of Kevin Love and his averages of 26 points and 13 rebounds a game. Love has been out for the last six contests after suffering a concussion.
The Pistons, who dropped their second straight and lost for the 40th time this year, were led by Tayshaun Prince with 18 points.