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Marcus Smart isn't going anywhere.

According to Shams Charania of Yahoo Sports, Smart and the Boston Celtics agreed to terms on a new four-year, $52 million contract.

The Celtics previously tendered a $6 million qualifying offer to make Smart a restricted free agent, which would have given them the right to match any offer sheet he signed with a competing club.

The sixth pick in the 2014 NBA draft, the 24-year-old has spent the past four seasons establishing himself as one of the NBA's most tenacious and relentless on-ball defenders.

While he's lagged behind as a scorer, averaging 9.4 points per game on 36.0 percent shooting from the field, he's compensated for those woes by becoming opposing ball-handlers' worst nightmare.

Not only has Smart averaged 1.5 steals a game dating back to his rookie season, but he's racked up 9.8 defensive win shares with no fewer than 2.2 in a given season. According to Basketball-Reference.com, he is one of 11 guards with at least 9.5 defensive win shares during that span.

Plus, the Celtics posted a stellar 99.4 defensive rating with Smart on the floor last season compared to a mark of 103.0 whenever he moved to the bench, according to NBA.com's lineup data.

"I've never had a coach from another team say anything but, 'That dude's a total winner.' Ever," Celtics head coach Brad Stevens said, per ESPN.com's Chris Forsberg. "When you watch him play on film, I think it's pretty obvious. He's a guy that you know impacts the game."

And that, above all else, is why the Celtics opted to retain him.

Moving forward, Smart should continue to operate as a defensive wrecking ball on the perimeter who can do the dirty work while Kyrie Irving, Gordon Hayward and Jayson Tatum slot into starring roles as the Celtics continue their pursuit of the franchise's first title since 2008.