Barcelona Open holder Casper Ruud ousted Hamad Medjedovic 7-5, 7-5 to reach the quarterfinals on Wednesday.
The Norwegian, ranked 10th in the world, conceded a break in the first game of the first set but pulled level at 4-4 with one of his own.
Ruud survived four break points for a 6-5 lead and then converted his third set point to take the first set.
The 26-year-old, a three-time Grand Slam runner-up, once again came from a break down in the second set to triumph, breaking to love against the Serb to wrap up his win.
Runner-up to Ruud in 2024, third seed Stefanos Tsitsipas steered into the quarterfinals with a 7-6 (7/4), 6-4 win over American Sebastian Korda.
The Greek came up against spirited opposition, with both players strong on their serve, but did not concede a break point in his straight sets win.
Tsitsipas will face Frenchman Arthur Fils, who breezed past Spain's Pedro Martinez in straight sets 6-3, 6-2.
Ranked 14th in the world, Fils conceded just one break point in the match, which the 20-year-old saved.
"I think (Fils) is a great competitor, I've played him twice and had no luck," said Tsitsipas.
"I'm going to change a few things compared to those two matches."
Holger Rune battled back from a set down to beat Sebastian Baez 4-6, 6-1, 6-2.
The world number 13 pulled out of Monte Carlo with food poisoning last week but roared back to defeat his Argentine opponent in three sets on the clay after a troubled opening.
Baez broke in the first game, consolidating for a 2-0 advantage and served it out to claim the first set, with Rune committing 15 unforced errors to 10 winners.
However, the Dane broke three times in the second set to get back on track and did the same again in the decider, converting his third match point.
On Thursday world No 2 Carlos Alcaraz will face Laslo Djere in another second round match, with the Spanish home favourite aiming for his third Barcelona Open title.