Andy Roddick pulled out a 6-4 3-6 6-3 win over Sam Querrey to advance to the Regions Morgan Championships semis.
Making his eighth quarter-final appearance at Memphis, top-seeded Roddick collected 11 aces, while the eighth-seeded Querrey powered 15 aces but also double faulted four times.
The world number six, Roddick continued his success in Memphis by converting two of his six break-point chances and winning 77 percent of his first-serve points.
Roddick, who is searching for his 27th career title and first since September in Beijing, won this event in 2002 and reached the finals on two other occasions.
To repeat those successes he will have to beat former world number 1 Lleyton Hewitt, who cruised to a 6-2 6-3 victory over Belgium's Christophe Rochus.