BOSTON -- Former Boston Celtics captain Rajon Rondo acknowledged Friday that he "hasn't played defense in a couple years," and suggested that the recent trade that delivered him to the Dallas Mavericks has reinvigorated him, particularly on the defensive end.

While addressing his return to Boston after Friday's shootaround at TD Garden, Rondo said what a lot of Celtics observers have long speculated: That his effort on the defensive end had waned, especially when the team dropped from contender status in recent seasons.

"I haven't played defense in a couple years," Rondo said. "I've been able to hide a lot with Avery Bradley on the ball. He's helped out, the young guy. But [in Dallas] they expect me to play defense and, in the West, if you don't play defense you'll get embarrassed every night at the point guard position."

Celtics coach Brad Stevens smiled when apprised of Rondo's comments, but declined to offer a response.

"I don't know the context of the discussion. I don't know the seriousness of his answer," he said. "I don't really have any reaction to that. He's a really good player, and I'm certainly not here right now to be critical or analytical of his comments to the media. I think, like everybody else, I'm excited for him that he's in a great opportunity and has a great opportunity in Dallas. I hope that we play well against him tonight."

The Mavericks are 5-2 since Rondo's arrival, including Friday night's 119-101 win against his old team. Rondo starred, scoring 29 points to go with six rebounds and five assists.

Entering Friday, the Mavs' defensive rating with Rondo aboard has improved by 4½ points while dipping from 105.1 points per 100 possessions over the first 28 games of the season to 100.6 in the six games since his arrival.