North Carolina - US qualifier Steve Johnson upset second-seeded Italian Andreas Seppi 6-7 (5/7), 6-4, 7-5 to reach the third round of the ATP Winston-Salem Open on Tuesday.
"Definitely played really well today(Tuesday)," said Johnson, a two-time US collegiate champion who needed two hours and 19 minutes to get past Seppi.
"Felt like everything I've been working on for the last four, five, six months kind of came together, so it's nice to see the hard work pay off in big situations."
The 23-year-old notched his fourth match win of the season and the seventh of his ATP career. He next faces Taiwan's Lu Yen-Hsun for a place in the quarter-finals.
Fish retired unwell, granting Finland's Jarkko Nieminen a third-round meeting with American Sam Querrey.
Nieminen was leading 7-5, 6-7 (3/7), 3-2 when Fish called it quits.
Fifth-seeded Frenchman Benoit Paire ousted Blake 7-6 (11/9), 2-6, 6-3 and seventh-seeded Fernando Verdasco rallied to beat Smyczek 3-6, 6-3, 6-3.
Paire next faces ninth-seeded Austrian Jurgen Melzer, who was up 4-2 in the third set when Thiemo de Bakker of the Netherlands retired with a toe injury.
Ricardas Berankis of Lithuania, ranked 126th in the world, dispatched Kudla 6-4, 6-4 in 63 minutes. Berankis will try to reach his third quarter-final of the season when he takes on Roberto Bautista Agut, who beat 14th seed Martin Klizan of Slovakia 6-4, 6-1.
Eighth seed Juan Monaco survived a second-round scare, battling past France's Nicolas Mahut 6-7 (4/7), 6-3, 6-4 in two hours and 26 minutes.
He next faces Alexandr Dolgopolov, who came back for a 4-6, 6-1, 6-4 win over Spain's Daniel Gimeno-Traver.
Russians Dmitry Tursunov and Alex Bogomolov jnr booked a third-round clash, Tursonov beating Belgian David Goffin 4-6, 7-5, 6-1 and Bogomolov beating lucky loser Joao Sousa 6-4, 6-1.
French 15th-seed Gael Monfils cruised into the third round, needing just 53 minutes to set down Guido Pella, 6-2, 6-2.
But fourth-seeded Spaniard Tommy Robredo fought off a determined challenge from France's Guillaume Rufin 7-6 (7/5), 4-6, 6-3.Results from the ATP Winston-Salem Open on Tuesday:
Ricardas Berankis (LTU) bt Denis Kudla (USA) 6-4, 6-4
Roberto Bautista (ESP) bt Martin Klizan (SVK x14) 6-4, 6-1
Jarkko Nieminen (FIN x11) bt Mardy Fish (USA) 7-5, 6-7 (3/7), 3-2, ret
Alex Bogomolov Jr (RUS) bt Joao Sousa (POR) 6-4, 6-1
Dmitry Tursunov (RUS x13) bt David Goffin (BEL) 4-6, 7-5, 6-1
Juan Monaco (ARG x8) bt Nicolas Mahut (FRA) 6-7 (4/7), 6-3, 6-4
Benoit Paire (FRA x5) bt James Blake (USA) 7-6 (11/9), 2-6, 6-3
Fernando Verdasco (ESP X7) bt Tim Smyczek (USA) 3-6, 6-3, 6-3
Jurgen Melzer (AUT x9) bt Thiemo de Bakker (NED) 7-5, 6-7 (4/7), 4-2, ret
Alexandr Dolgopolov (UKR x10) bt Daniel Gimeno-Traver (ESP) 4-6, 6-1, 6-4
Steve Johnson (USA) bt Andreas Seppi (ITA x2), 6-7 (5-7), 6-4, 7-5
Gael Monfils (FRA x15) bt Guido Pella (ARG) 6-2, 6-2