The Pole, however, had to overcome a first-set surge from Mertens, who rallied from 5-2 down to level at 5-5, but could not continue her momentum in the tie-break. (More Tennis News)
Mertens had seemingly used up all her energy in the opening set, with Swiatek able to take control of the match and seal the victory in one hour and 48 minutes.
"In the first set, my serve wasn't working perfectly," Swiatek said in her on-court interview. "I'm glad I was patient enough to just work for it, and in the second set I felt much better.
"I love playing here. I missed playing here in 2023, so I wanted to enjoy every day here and not take it for granted.
"Today's match was nice because we had some tight moments as well, and I was able to play well through them, so I’m pretty proud and looking forward to the next one."
Swiatek will now face Elina Svitolina in the next round after the Ukrainian beat Karolina Muchova 6-2 3-6 6-2.
Data Debrief: Swiatek survives serving struggles
Having failed to lift a WTA title in the first five events she has taken part in this year, Swiatek showcased her resilience and power to earn a milestone victory, though it did come with its issues against Mertens.
In the first set, Swiatek only won 43% of the points behind her second serve, allowing Mertens to claw her way back in the contest. However, the second seed was able to resolve the issue in the second, raising her first-serve percentage from 60% to 79%, missing only four of her first deliveries.
But her imperious record at the early stages of tournaments is impressive. Indeed, after notching her 25th consecutive round of 16 appearances, she is clear of anyone in the field. Maria Sharapova is second on the list with 18, tallied between Indian Wells in 2011 to Rome in 2013.
