Juan Martin Del Potro Not Focused On Catching Rafael Nadal, Roger Federer

Juan Martin del Potro is not focused on catching Rafael Nadal and Roger Federer in the Association of Tennis Professionals tennis rankings.

Del Potro is experiencing his best-ever start to a year with victories in the Mexican Open in Acapulco and most recently defeating Federer in the final at Indian Wells earlier this month.

The Argentine most recently defeated Canada's Milos Raonic in the Miami Open quarterfinals on Wednesday night and will face American John Isner in the semifinals Friday.

Currently riding a 15-match unbeaten run, Del Potro, ranked sixth in the world, seems to finally be playing at the level most expected of him after being dogged by injury problems previous years.

A win in the Miami Open would not only help him complete the "Sunshine Double" but also give him 955 points, taking him to a career-high world No. 3.

Although such a feat would put him just behind current world No. 1 and 2 — after the rankings are updated next week — Nadal and Federer respectively, the 29-year-old claims catching the legendary duo is not his main goal.

"It's not my main goal, but if I can improve it's always better," Del Potro said, as per Express. "I am the world No 6 and I think I wouldn't have imagined to be the number six being that close to retirement."

"What I am doing seems to be normal, but it's not a little thing. I know better than anyone what it's costing me, all the days there is something new but I don't want to stop. If I was home since 15 days ago I wouldn't have pain; I prefer to be here this way."

Elsewhere in the Miami Open, world No. 5 Alexander Zverev defeated Croatia's Borna Coric in straight sets Thursday to reach the semifinals.

The German youngster will face Spain's Pablo Carreno Busta next, who defeated 2017 US Open finalist Kevin Anderson in the other quarterfinal.

"I think he's [Busta] playing very well right now. He played well in Indian Wells, and is playing well here," Zverev said. "It doesn't get any easier, but it's a Masters. We know it's not going to get easier, and I'm looking forward to it."

Meanwhile, 2017 US Open women's champion Sloane Stephens is on course to winning her first-ever Masters 1000 final after coming from behind to defeat Victoria Azarenka in a 3-6, 6-2, 6-1 win in Key Biscayne.

"I knew I had to stay in it. Victoria is a great champion," Stephens reflected. "I kept battling and I got a little momentum going in the second set. Growing up in South Florida, this is so incredible to be in the final. I knew I had to focus on my side of the court and be solely focused on myself."

The American will face 2017 French Open winner Jelena Ostapenko in the final Saturday after the Latvian defeated Danielle Collins, a qualifier who had shocked Venus Williams in the quarterfinal stage.