Atlanta have advanced to a second round NBA playoff match-up with Cleveland after eliminating Boston with a 104-92 victory in game six.
Paul Millsap had 17 points and eight rebounds while Al Horford and Kent Bazemore each scored 15 for Atlanta, who led by as many as 28 in the second half.
It was Atlanta's first playoff series win over Boston in nearly 60 years, and will go on the road for the opening game of their series against the Cavaliers on Monday.
The Hawks lost all three meetings with the Cavaliers during the regular season by an average of 9.7 points, Cleveland having also swept Atlanta when the two teams met in last season's Eastern Conference finals.
Isaiah Thomas had a double-double with 25 points and 10 assists for the Celtics, who shot just 36.2 per cent from the field on Thursday night.
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While the Hawks and Cavs have already advanced, Toronto and Charlotte can do the same on Friday should they close out their respective series' against Indiana and Miami.
Also on Friday, the surprising Portland Trailblazers can book a second round match-up with Golden State in the second round of the Western Conference playoffs with a win in game six of their series against the LA Clippers.
