As his style, Kelly Olynyk greeted the Miami media rocking the customary backward baseball cap after practice Friday. The sun beamed through the Heat’s practice facility on this October day, quite a contrast from those cold winter days in Waltham. Olynyk will face what’s left of his former team Saturday when the Heat host the Celtics. Only four players from Olynyk’s 2016-17 team remain — Al Horford, Jaylen Brown, Marcus Smart, and Terry Rozier — but his memories of his four years in Boston are strong. And his bond with coach Brad Stevens is even stronger. When Olynyk’s contract was going to be renounced for the Celtics to make room to sign Gordon Hayward, Stevens talked the big man through the entire process, offering all the possibilities. When Olynyk returned to Boston for a charity event in September, he and Stevens hugged tightly and carried on a long conversation. What’s more, Stevens called Olynyk just a few days ago to check on his progress in Miami. “It’s fun, kind of gives you a little extra excitement and purpose for the game,” Olynyk said of Saturday. “It’s fun just to get an opportunity to go out there and play and they’re a great team, so it’s a great test for us.” Olynyk harbors no ill feelings about how it ended in Boston. He’s too laid back to ever carry grudges. The Heat quickly signed him to a four-year, $50 million contract to become one of their top reserves. Through four games, he is averaging 9.5 points and 6.5 rebounds in about 22 minutes per game. His Celtics’ numbers were strikingly similar.