Phil Pressey is a point guard, and thus prone to a miserable time in summer league competition. He needs chemistry, teammates willing to play together, to thrive. Thankfully for Pressey, Kelly Olynyk has a clue. “This guy back here, he thinks like a guard, and that makes it a lot easier on me,” Pressey, the Celtics free agent via Missouri, said with a nod in Olynyk’s direction yesterday following a 95-88 loss to the Magic on the first day of the Orlando summer league. But this is why president of basketball operations Danny Ainge traded up to draft the Gonzaga center with the 13th pick. Olynyk was the most offensively skilled center on the draft board — miles ahead of Nerlens Noel and even Alex Len in terms of his ability to see the floor. All of that vision and polish came out in Olynyk’s first game in a Celtics uniform. He not only scored 25 points on 9-for-12 shooting, hitting from a shot chart’s worth of spots, he also laced passes out of the high post and generally boosted the floor’s overall IQ level.