Juan Martin del Potro claimed his 17th consecutive win on Friday to progress to the semi-finals of the Legg Mason Classic - but top seed Andy Roddick was eliminated in the last eight.
While Del Potro came into this event riding a sudden wave of success, world number nine Roddick, who lost to the Argentine in Los Angeles last weekend, had an impressive track record here that dated back seven years.
However, the duo experienced contrasting fortunes with second-seeded Argentine Del Potro defeating John Isner 6-4 6-4, while Roddick fell 0-6 6-2 6-4 to Viktor Troicki.
Roddick won the championship in 2001 and 2005 and has a 25-4 lifetime record in the tournament.
Having skipped the 2006 event, he had won his last 12 matches here, including a trying 4-6 6-4 7-6 (7/2) triumph over Eduardo Schwank in the second round on Thursday.
Roddick appeared on track for a rematch of the Los Angeles final with Del Potro after blitzing Troicki 6-0 in the first set but the top-seeded American continued his erratic play, dropping the final two sets en route to lose in one hour 41 minutes.
Troicki next will face world number 84 Igor Kunitsyn, who defeated 314th-ranked Somdev Devvarman 6-4 6-1 in one hour 23 minutes to reach the semi-finals.
The 6ft 6in Del Potro is not used to looking up to many players on the ATP circuit. But that was the case against the 6ft 9in Isner, who is the second-tallest player on tour behind Croatia's Ivo Karlovic (6ft 10in).
Del Potro won his first career ATP singles title in Stuttgart last month and has been rolling ever since.
He also claimed championships at Kitzbuhel and Los Angeles during the 17-match winning streak. The impressive run has shot the 19-year-old from 65th to 19th in the rankings and his record has improved to 25-8 after a mediocre start to the year.
Up next for Del Potro is a last-four meeting with fourth seed German Tommy Haas, a 7-5 6-1 victor over Colombia's Alejandro Falla.
