Aryna Sabalenka was forced to go the distance again at the Madrid Open as she battled past Robin Montgomery on Sunday.

Sabalenka, the reigning Madrid Open champion, needed three sets to win her second-round tie against Magda Linette on Friday, and the second seed did not have an easy ride against American Montgomery.

However, she eventually got over the line, triumphing 6-1 6-7 (5-7) 6-4 to tee up a last-16 meeting with Danielle Collins, who defeated Jaqueline Cristian 3-6 6-4 6-1.

Collins has now reeled off 15 straight wins, having won the Miami Open and Charleston Open in recent weeks, and has progressed to the last 16 in Madrid for the first time in her career.

The American said: "I've been doing so well the last couple of weeks, I think the girls know that when they come out and play me, they've got to go for it. 

"That certainly was taking place the last two matches, some big shots that I've had to counter, and be able to react quickly."

Data Debrief: Sabalenka up there with Serena

Sabalenka has now won 14 of her 17 matches at the Madrid Open, which she won in 2023 and 2021.

Since the inception of the tournament, only Serena Williams (15) has won more of her first 17 matches at the event.