Top seed and two-time finalist John Isner will face former world No. 1 Lleyton Hewitt in the semifinals at the BB&T Atlanta Open.

Isner fired 21 aces while edging fellow American James Blake in a pair of tiebreaks, 7-1 and 7-5. The towering right-hander was a runner-up at this tournament in 2010 and 2011, losing to countryman Mardy Fish both times.

Meanwhile, the seventh-seeded Hewitt fought back from a set down and finished strong in a 1-6, 6-3, 6-0 victory over third-seeded Croat Ivan Dodig in the first quarterfinal on Friday.

The Aussie beat Isner in three sets two weeks ago in the Newport semifinals.

Second-seeded South African Kevin Anderson and American Ryan Harrison will meet in the other semifinal.

Anderson outlasted Uzbekistan's Denis Istomin by a 6-3, 3-6, 6-3 score, while Harrison battled past Colombian Santiago Giraldo, 6-3, 3-6, 7-6 (7-2).