Lleyton Hewitt showed all his trademark grit to defeat Blaz Kavcic at the SAP Open in San Jose, while Fernando Verdasco crashed out.
The 31-year-old Australian trailed by a set and a break against an opponent six years his junior, but pulled a vintage performance out of the hat to defeat the 79th-ranked Slovenian 3-6 6-4 7-6 (7-4) in two hours and 35 minutes.
It was Hewitt's first win over Kavcic in three career meetings and he was delighted to set up a clash with American third seed Sam Querrey in the second round of the ATP 250 tournament.
"It was a tough match," Hewitt said. "There were a lot of momentum changes throughout the match.
"He's a tough player and competitor out there. He's had a pretty good start to the year as well. It wasn't easy. In the end, I was happy to get through."
Hewitt was not the only Australian to move into the second round on Tuesday, with seventh seed Marinko Matosevic progressing at the expense of American Jack Sock 7-6 (7-5) 6-1.
In other first-round results, fifth seed Verdasco was bundled out by American qualifier Tim Smyczek 6-3 6-3, but sixth-seeded Uzbek Denis Istomin had few problems moving through, defeating Ryan Sweeting 6-3 6-4.
Istomin's opponent in the second round will be German Benjamin Becker, who accounted for American Ryan Harrison 6-7 (3-7) 7-5 6-3.
Canadian Vasek Pospisil teed up a showdown with second seed John Isner by defeating Russian world number 73 Evgeny Donskoy 7-5 6-1.