Jayson Tatum’s strong start, Kemba’s comfort level and other takeaways from Day 1 of Celtics training camp

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(Maddie Meyer/Getty Images)

The Celtics kicked off their first day of training camp at the Auerbach Center on Tuesday in the first of several double sessions before their preseason opener on Sunday at the TD Garden. Co-owners Wyc Grousbeck and Steve Pagliuca were on the scene for the initial session, along with observers that included Tommy Heinsohn and former Kings coach Dave Joerger. A host of takeaways from the session that went over two hours in length.

1. Defense is the top priority out of the gate: The Celtics were a top-10 defense on paper in the regular season but that side of the floor betrayed them against the Milwaukee Bucks in the postseason, as they allowed an average of 117 points in the final four games of their 4-1 series defeat. As the page is turned to a new season in Boston, Brad Stevens is starting camp looking to re-establish the team’s identity on the defensive end.

“From a technical standpoint, obviously you want to create a defensive mindset and mentality,” Brad Stevens explained. “I think that’s the best way to create a team mindset. I thought our guys did a good job of picking up stuff quickly. We got a lot in the first day and we’ll be able to take the film later this afternoon and talk about how we’re going to improve and get ready for tomorrow.”

“Defense is always a key,” Jayson Tatum added. “And effort and being together. It’s only day one but everybody got a good feel. We’ve got to get through our practice and get a feel for each other. There’s a lot of new faces.”

With a mix of new and inexperienced rookie personnel in the fold, Stevens will have to tread carefully as he