By Chris Oddo

(February 28, 2013) -- Ernests Gulbis, sporting a retooled forehand and all the trappings of drama that we've come to expect, slipped past a stumbling Sam Querrey and into the Delray Beach quarterfinals on Thursday, 6-4, 4-6, 7-6(4).

Gulbis, a qualifier at the scene of his first career title in 2010, looked to be down and out when he trailed the third-seeded Querrey 4-0 in the third set, but a spirited comeback aided by some untimely double-faults from the American enabled him to get the win.

"I was really pissed off that I couldn't close the second set," Gulbis said in an on-court interview with Ashley Fisher immediately after the match. "I lost my concentration. I was just mad at myself." Gulbis, a former champion in Delray Beach (2010), smashed a racquet after double-faulting in the second set, and also received a warning for cursing after another point. "Everybody likes it, it's part of the fire in the game," Gulbis told reporters afterwards. "I think tennis lost a little bit of its fire. Which interesting players do we have nowadays?"

The World No. 109 staged a nice rally to get close to Querrey in the final set, then Querrey helped him get even. The American double-faulted on break point while serving for the match, and in the tiebreaker, he finished with two more ill-timed double-faults, the last on match point. "I'm pretty bummed," he would later say. "At 5-4 I was tentative on some shots. The double-fault killed me. It's a 50-50 match from there."

No. 2 seed Tommy Haas advanced later in the afternoon with a command serving performance over Denis Istomin, 6-4, 6-1. Haas lost only two first-serve points in the match.

Top-seeded also advanced, taking out Japan's Go Soeda 7-6(2), 6-2 with a 15-ace performance. Isner will face reigning champion Kevin Anderson of South Africa in Friday's quarterfinals. Anderson took out Yen-Hsun Lu, 6-4, 3-6, 6-3.

In other round of 16 action at Delray Beach, lucky loser Ricardas Berankis took out promising American Jack Sock 3-6, 6-4, 6-1.