CHARLESTON, SC, USA - Andrea Petkovic just can't stop learning. The 31-year-old German views her tennis in a different light these days, one that sees her using the sport more for self-improvement than for acclaim. 

The 2014 Volvo Car Open champion told reporters the biggest difference between the Petkovic who won the biggest title of her career here 5 years ago and the one who grit her teeth through cold conditions to defeat Varvara Lepchenko 6-0, 6-4 in the first round on Tuesday to secure her second main draw win of the season is how tennis is no longer the end all be all, but a means to an end.  

"I think the biggest difference, what I'm trying to work at now, is sort of using tennis as a tool," Petkovic said. 

"I think I've achieved so many things. If I was to retire today, I would be happy. I still want to achieve much more, but I would be satisfied.  Not happy, but I would be satisfied, and I think I could look back at a good career.

"Now I think tennis is more of a tool for me to evolve as a human and as a personality, because there are still so many things where I'm so stubborn and just sometimes think I'm smarter than everybody else just because I read two books in my life, you know? 

"Those are the things that I try to change, and tennis is a tool for me to achieve that, where I have to listen to others and I have to sort of be open-minded and just evolve every day. In tennis, when you don't do that, you get the cost right away, you know? You have to pay your debts. 

2014 champion Andrea Petkovic arrives at the 2019 Volvo Car Open player party. (@Jimmie48)

"So that's what I like about tennis. When you do the right things, also you get a reward.  Maybe not right away, but it pays off at one point, and I've been through so many ups and downs in my career that I know that." 

"So now tennis is sort of a tool for me to just evolve my personality and work on these things that are still my weaknesses somehow." 

That quest to evolve and improve has led the 31-year-old German to what some might consider an unlikely source of inspiration: The NFL. 

Petkovic has been reading New England Patriots quarterback Tom Brady's health-oriented book, TB12: How to Achieve a Lifetime of Sustained Peak Performance, and said the book spoke to her, athlete-to-athlete. 

"I think it was just the fact that he's stayed healthy for so long," Petkovic said, when asked what compelled her to pick up Brady's book. "I mean, I get it. For fans, it's amazing to read about somebody like Roger or Rafa who won Grand Slams when he was 20 and who was amazing when he was 18. 

"But for me, as an athlete, it was much more inspiring to read Tom Brady's story where he was average for most of his life and through his work ethic and trying new things and being open-minded and letting advisors in and making the right choices, he became one of the greatest in his sport. 

"I think that's what's inspiring to me as an athlete, that somebody who was never thought of as this, like, incredible genius somehow made it work." 

"I'm feeling really good. I think Tom Brady would be proud of me because I bought his book and I'm reading it thoroughly. He drinks 250 ounces of water a day.  My hydration level is I have to pee every three seconds, so still far away from Tom Brady. I don't know if I can match him.  

"But he has some good tips, so I think I really have my body in check so far, hopefully. And, yeah, we'll see how much longer."