PHOTO: Jalen Johnson (1) in a preseason scrimmage By TOM SHANAHAN Jalen Johnson came to Duke for the chance to learn from basketball sensei Mike Krzyzewski and enjoy the marquee games. He's expected to open the season as a starter for the blueblood program after he was named a preseason All-ACC first-team pick. "If you're playing for Duke basketball, there aren't many bigger blessing than this. " said Johnson, a 6-foot-9, 220-pounder from Milwaukee. I'm just going to…