OKLAHOMA CITY — Over the course of NBA history, there have been impressive coaching performances.  Rick Carlisle inserting J.J. Barea into the Mavericks’ starting lineup in the middle of the 2011 NBA Finals against the Heat’s “Big 3” is one.  Lakers coach JJ Redick has led the franchise to back-to-back 50-win seasons. Getty Images Trailing 2-1 to the Cavaliers in the 2015 NBA Finals before Steve Kerr inserted Andre Iguodala into the Warriors’ starting lineup is another. But for Lakers coach JJ Redick, defeating the reigning champion Thunder in the Western Conference semifinals without Luka Doncic might top them all.  Redick has shown promise in his first two years as a head coach at any level. He’s guided the Lakers to back-to-back 50-win seasons. He led the wounded Lakers to a first-round upset over the Rockets without his leading scorers. That’s not accidental. That’s real coaching.  But beating the reigning champion Thunder? This assignment is different.…