Latvian Gulbis, who became the first qualifier to clinch an ATP title this season with his victory at Delray Beach last month, fought back to beat Italy's Andreas Seppi 5-7 6-3 6-4 in a contest lasting just over two hours.
Ranked 67th in the world, qualifier Gulbis said he fancied his chances as he aims to keep his winning run going against Nadal, an 11-times Grand Slam singles champion who has twice triumphed at Indian Wells.
"I think the way I play right now, that should make a difference," the 24-year-old told reporters after improving his record against Seppi to 4-0. "I believe that I can win.
"I want to play as many as matches as possible against these top guys. Sooner or later I'm going to win something and it's gonna give me extra confidence.
"I need to win against the guys who are ranked 20 to 100 easier than I did, let's say today, and then I need to have enough shots against the big guys."
Prodigiously talented Gulbis, whose brilliant shot-making is often undone by a slew of errors, has won three career ATP titles and certainly does not lack self-belief.
Though beaten by Nadal in all four of their previous meetings, the Latvian relished the Spaniard's all-action style with his typically high-bouncing style.
"I like to play against him because his ball and his heavy spin, it's good for my timing," said Gulbis. "I like the opponents who hit spin, high balls. It's easier for me to control them.
"I had three sets (against him) twice, and just in the third set lack of experience, lack of fitness, lack of everything and then he just broke me down.
"You know, when I play him now I know how he plays. And of course he's a great player, but I honestly believe that if I play my best game I can beat him."
Nadal, continuing his comeback after being sidelined for seven months last year by a left knee injury, was gifted a spot in the last 16 when Argentina's Leonardo Mayer withdrew with a back injury before the start of their third-round match.
- Sports & Recreation
- Andreas Seppi