SAN ANTONIO — San Antonio coach Gregg Popovich missed the Spurs’ game Saturday night against the Minnesota Timberwolves because of an undisclosed illness.Assistant coach Mitch Johnson took over the head coaching duties. Johnson said he was informed about 2 1/2 hours before tipoff that Popovich, 75, was unavailable.”He’s not feeling well,” Johnson said. “This has happened before. I think everybody’s just always got to be ready for the next man up. We’ve had it with injuries and sometimes people get sick or don’t feel well or things come up in life. He’s just not feeling well.”Popovich is the NBA’s career leader with 1,390 victories and another 170 postseason wins while winning five NBA titles. He is in his 29th season, all with San Antonio.