ATLANTA - Paul Pierce collected 26 points and nine rebounds and Rajon Rondo posted a triple-double as the Boston Celtics locked down on defense in the second half to rally from a 19-point deficit and post an 89-81 win over the Atlanta Hawks on Saturday.

Rondo piled up 14 points, 11 boards and 10 assists for his second triple-double of the season and the 15th of his career.

Kevin Garnett added 14 points for the Celtics, who have won two straight since a four-game losing streak.

Lou Williams scored 21 of his game-high 28 points in the first half for the Hawks, who have lost two straight. Jeff Teague added 17 points and Josh Smith contributed 12 points and 10 rebounds for Atlanta, which shot just 25 percent from the field in the second half after hitting 53 percent in the first.

The Hawks led by as many as 19 in the first half and took a 53-38 advantage into the locker room before their third-quarter meltdown.

Atlanta managed just two field goals in the quarter, and Boston closed the period on a 16-2 run to take a 71-62 margin into the fourth. Atlanta pulled with 79-74 on Ivan Williams' follow dunk with 5:35 left, but the Hawks came up empty on their next three trips and the Celtics pushed it out to 85-74 and coasted to the finish.

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NOTES: The Celtics swept a back-to-back set for the first time this season - they also won at home against Indiana on Friday. ... Two of Rondo's last three triple-doubles have come against the Hawks. He also notched one against Atlanta on April 11, 2012. ... Atlanta C Al Horford was limited to six points on 2-of-8 shooting, only the third time in 31 games this season he has failed to score in double figures.