Blake stuns Nalbandian in Washington
American Blake, champion at the William H.G. FitzGerald Tennis Center in 2002 and runner-up three years later, sent the eighth seed packing with a 6-2 6-4 win to reach the third round for just a second time in 10 tournaments this season.
The current world number 90 will now play compatriot John Isner in a mouth-watering tie after the 11th seed downed Tobias Kamke of Germany 6-1 6-3.
Sweeting made light work of his compatriot in the first set on Grandstand Court before gaining the upper hand in the second and closing out a straight-set win.
Wild card Ryan Harrison progressed into the second round after the American downed Germany's Mischa Zverev 6-4 1-6 6-1 on Stadium Court. A meeting with Viktor Troicki awaits.
Also moving on at the tournament in Rock Creek Park were Italian Flavio Cipolla, who beat Marsel Ilhan of Turkey 7-5 6-0, and Germany's Michael Berrer, a 7-5 6-1 winner over Paolo Lorenzi, another Italian.
German Tommy Haas overcame Fernando Gonzalez of Chile, India's Somdev Devvarman beat Denis Gremelmayr of Germany and Bulgarian Grigor Dimitrov saw off Tim Smyczek of the States to complete the day's action.