Sam Querrey safely reached the last 16 of the BB&T Atlanta Open but two American hopefuls failed to qualify for the first round.
While the 26-year-old from Las Vegas beat compatriot Steve Johnson 7-6 (7/3) 7-5 to progress at Atlantic Station, Alex Kuznetsov and Kevin King were denied entry to the main draw.
Kuznetsov was ousted by Illya Marchenko, who won 6-3 3-6 6-3, while Australia's John-Patrick Smith put together a comfortable 6-2 6-1 victory over Peachtree City's King.
Colorado-born Rajeev Ram also looked like heading out but was given a lucky loser's spot despite slumping 5-7 6-3 7-5 against Michael Venus.
Ram, the one-time world number 78, must next face sixth seed Denis Istomin of Uzbekistan.
Canada's Steven Diez was leading Thiemo de Bakker by one set when the Dutchman retired injured and the Toronto native will now tackle second seed Kevin Anderson.
Querrey will next play Israel's Dudi Sela, who ended the hopes of another American Donald Young in a 6-3 6-0 triumph.