Kevin Durant has OKC on top right now.A week ago, many observers were anointing the San Antonio Spurs as the eventual NBA champions. They were unspectacular, but sharp, and had won 20 games in a row, including two to open the Western Conference finals against the Oklahoma City Thunder.Now, the Spurs look like a team on the way out, passed swiftly and deftly by a young Thunder team that was, as TNT analyst Steve Kerr astutely noted Monday night, “growing up before our eyes.”That might sound trite, but it also was completely apropos considering what OKC did in Game 5 Monday night in San Antonio. In short, the Thunder stunned the Spurs, 108-103 to take a 3-2 series advantage.OKC can advance to the NBA Finals for first time since moving to Oklahoma City from Seattle three years ago with a victory in Game 6 Wednesday night at home in a game that will have the city on fire.Monday, OKC confirmed that it has figured it out. It was one thing to come together and win Games 3 and 4 at home. But to go into the AT&T Center and play with enough poise and share the basketball, well, it signaled another level of maturity – and that was all the young and athletic team has been missing.“They are hard to guard, talented, hungry, athletic,” San Antonio coach Gregg Popovich said. “I thought we spotted them 24 minutes. We didn’t compete in the first half and they competed for 48 minutes. . . We don’t get that straight, it’ll be over on Wednesday.”Again, it was Kevin Durant (27 points) who led OKC’s surge, with a huge hand from Sixth Man of the Year James Harden. After getting just one shot in the first two quarters, Durant, the superstar forward, erupted in the third and fourth quarters, fashioning an array of shots. The Thunder overcame a slow start to both halves of the game with explosiveOKC led by 14 in the fourth quarter after a four-point play by Harden (20 points). It looked to be over then, but suddenly Oklahoma City reverted to point guard Russell Westbrook (23 points, 12 assists) dribbling aimlessly around the perimeter, stalling the offense.San Antonio took advantage and scored 11 straight to cut it to 101-99 with 1:37 to play. Westbrook and Tim Duncan (18 points, 12 rebounds) traded baskets before the biggest shot of the night – a step-back three-pointer with 28.8 to play by Harden to put the Spurs in front, 106-101.Manu Ginobili, who started and was brilliant with 34 points, made a layup and OKC turned over the ball, giving San Antonio a chance with 15 seconds left to tie it with a three. However, Ginobil, who made five threes, missed, and that was that. OKC had gained control of the series.“Heartbreaking,” Duncan said.