NEW YORK, NY, USA - Some see her as defending champion. As good as she's played thus far, Sloane Stephens says she's just another player among the last eight at the US Open.

Read more: Stephens settles into starring role as US Open defending champion

"I think defending a title is super tough," she said after a straight-forward win over No.15 seed Elise Mertens. "It doesn't happen very often. I think the expectation to come in here and win the tournament is just ridiculous. You have to take one match at a time."

Stephens proceeds to deconstruct the definition of - and what it means to be - a defending champion, citing too many experimental variables for it to be a true comparison.

"Defending a title isn't defending," she explains. "If you were to play the same people in a row again and beat all of them again, that would be defending your title. When you're playing a whole new draw, different seedings, different ranking, there's so much that goes into it. When you go to a tournament, it starts all over again."

"You can only focus on things you can control: 'Yeah, I'm nervous, but I can still move my feet.' 'Yeah, I'm nervous, but I can still hit my serve over 60 miles an hour.' Focusing on those little things definitely helped me in the earlier rounds."

- Sloane Stephens

Still, she insists, it's not something she's over-thinking.

"I think I try not to put too much emphasis on defending the title, just try to come in and win as many matches as possible, like keep playing, keep going."

Hypothetical aside, the hometown hero admitted to feeling some pressure throughout the first week, particularly against Anhelina Kalinina, an unfamiliar opponent in oppressive weather on Wednesday.

"In the first couple rounds I was super nervous. Not because I didn't know my game was there, it was because of the moment: 'You were here last year, you did something so great. What's going to happen now?'

"You can only focus on things you can control: 'Yeah, I'm nervous, but I can still move my feet.' 'Yeah, I'm nervous, but I can still hit my serve over...60 miles an hour.' There's things you can do to control the moment. Focusing on those little things definitely helped me in the earlier rounds."

Back into the quarterfinals, she'll have a chance to prove a part of her earlier hypothesis as she faces none other than Anastasija Sevastova, whom she outlasted in a third set tie-break in this exact round one year ago.

"I think it will be a good match. I played her in Montréal," she said, referencing her 6-2, 6-2 win en route to the Coupe Rogers final. "We played a good match. I'm hoping to just get out there and kind of execute the same game plan. It obviously won't be easy; the quarterfinals of a Grand Slam is always really tough.

"It's big opportunity for both of us; I'm just excited to get out there and compete again. Being defending champion, being able to get to the quarterfinals again, is incredible. I'm just going to try to keep building on that and keep going."

The World No.3 has made oblique references to taking the top spot on the WTA rankings throughout the summer; her runner-up finish in Montréal and a strong result here would make the mission all the easier in Asia, where she defends next to no points. 

"I want to get my ranking as high as I possibly can. Coming in here I was No.3. I want to keep going. There's only two more spots to go, but you still got a lot of work to go.

"It's something new. I've never had that type of challenge before. I think now it's something really cool, something to look forward to. I'm excited about where my game is, about competing, being on the court."

Stephens commands the press room, setting the timer on her phone to ensure things don't exceed 10 minutes. It's something else she can control, unlike the surreal feeling of having already won a US Open title.

"I never really say it out loud. When you put it in context so people will understand, you have to say it. It's kind of weird. I'm grateful to be able to have won last year, take in a really great opportunity and make it into something.

"I've only seen my trophy once or twice. It's at my grandparents' house, in their dining room. They see it every morning, show all their friends. Literally everyone in my family has sent me selfies of them with the trophy. It's safe and sound, gets a lot of love. It's pretty cool, something to have that's really amazing, something I'll remember for the rest of my life, show my grandkids."

If one title is surreal, imagine two.