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The Boston Celtics extended their winning streak to four games and became the first team to clinch a playoff spot this season with their 127-112 victory over the Phoenix Suns on Thursday night. It was a defensive play by their head coach, Joe Mazzulla, though, that had everyone talking in the end. 

Late in the fourth quarter, Jaylen Brown picked off a pass from Grayson Allen and threw down a huge slam to put an exclamation point on the win and force a timeout. As both teams were walking to their benches, Suns forward Royce O'Neale tried to take a 3-pointer, as players often do after the whistle. 

Mazzulla wasn't having it. He lunged out with a strong contest on O'Neale, whose effort clanged off the rim. 

After the game, Mazzulla explained his defensive effort:

"I saw a guy going in to try to get a shot and he hadn't made one and I didn't want him to feel good about himself going to the bench," Mazzulla said. "[Boston Globe writer] Gary [Washburn] asked me about that a month ago and that's a bench rule. Guys don't shoot shots in front of our bench to go back to their bench to feel good about themselves. If I'm gonna ask the guys to contest, the staff's gotta do the same. 

"At the end of the day, it's about the mindset and the approach that we bring, and it's within the rules of the game. It's about setting a tone, and it's just that. One of the biggest pet peeves is thinking that a guy's gonna get a free shot and that's not the way it works. If we're gonna hold our team to a standard, we hold our staff to the same thing. There's been times where we've missed it and I've held the staff accountable to it, and we've gotta do the best job we can of not doing it."

Players blocking opponents' shots during dead ball situations is nothing new. Former Celtics star Kevin Garnett was so insistent on doing so that there's an entire highlight reel on YouTube of his blocks after the whistle. 

A coach getting into the mix, however, now that's notable. 

"Joe being Joe," Jayson Tatum said. "That's who Joe is. When he did it, I wasn't caught off guard. I expect him or one of the coaches to do that. Gotta love Joe for Joe." 

The Celtics have the No. 2 defense in the league this season and allow just 110.4 points per 100 possessions, which is a big reason why they are 52-14 and six games ahead of everyone else in the league. If antics like this from Mazzulla help them stay locked in to maintain that form, then more power to him.