Marcus Smart is feeling like a new man after losing 20 pounds during the offseason.

Smart, who is one of only four returning players from last year's Celtics roster, told Abby Chin and Brian Scalabrine he "feels amazing" after making weight-loss his priority over the summer.

As for what made Smart decide to make that commitment, he said nagging back pain during the playoffs gave him no choice.

Throughout the playoffs I was having really bad back pains...  It was really hard for me to move. My back was killing me during games, before games, after games. I just knew something had to change.

Apparently, the change made all the difference. 

I feel amazing. I feel like I can get by anybody. I feel like I can actually get to the rim a lot more.

Not only does Smart expect a positive change on the offensive end, he also sees cutting from 240 to 220 pounds helping the area he prides himself on: His defense.

I was 240 [pounds] trying to guard guys like John Wall and Kyrie Irving. That's not going to work.

Fortunately, he won't have to worry about guarding Irving again any time soon. But Smart's confidence in the ability to do so heading into the new season bodes well for his chances to improve his game.