Donald Young came from a set down to upset Juan Monaco tor each the quarter-final of the US Clay Court Championship in Houston.
The 24-year-old American, who will now be making his first appearance in the last eight of a clay tournament on the ATP Tour, toppled sixth seed Monaco 6-7 (7-4) 6-4 6-3.
Young told atpworldtour.com: "I've never won two matches in a row (on clay). It's a big win for me and I'm just happy to move through."
Fellow American Jack Sock also reached the last eight with a 6-4 6-3 victory over Benjamin Becker but in-form Steve Johnson was knocked out 6-0 4-6 6-3 by fourth seed Fernando Verdasco.
Colombian Alejandro Gonzalez reached his first ATP Tour quarter-final when fifth seed Feliciano Lopez pulled out while trailing 6-3 2-0.
However second seed Tommy Robredo made a shock exit as he fell to a 6-3 6-4 defeat to Santiago Giraldo but compatriot Nicolas Almagro, ranked No 3 at the event, progressed with a 6-2 6-3 win over Michael Russell.