Green Bay quarterback Aaron Rodgers and wide receiver Marquez Valdes-Scantling stood together on the sideline last month at Cincinnati admiring the work of De’Vondre Campbell. The Packers’ new inside linebacker had nine tackles, broke up a pass, and snared another that day, helping Green Bay edge the Bengals. “We just said, ‘How in the hell was this guy on the street?’” Rodgers recounted. “It’s a great pickup by our personnel folks. He can run, he’s a great tackler, he’s around the ball all the time, he’s a great locker room guy. I mean, it’s baffling to me.” When Packers GM Brian Gutekunst signed the sixth-year pro to a one-year, $2 million contract in June, it appeared a minor move even though Campbell had 70 starts in four solid but unspectacular seasons with the Falcons and one with the Cardinals. Instead, he has become a key reason for Green Bay’s 7–2 …