By Hunter Hodies Charles Barkley isn’t happy with how Kevin Durant has played for the Brooklyn Nets these last three games. The Nets are down 3-0 in their series against the Boston Celtics and face elimination on Monday night. Durant hasn’t been himself in this series. He finished Saturday night’s loss with only 16 points and is only shooting 36.5% from the floor. Barkley expects more out of Durant, especially during this time of year. “All these guys can play, but please don’t tell me that you’re a great, great player and you’re averaging 20 (points per game),” Barkley said. “I don’t think I …