It has been a career-defining year for Simona Halep. The 27-year-old has enjoyed her top-ranked perch since winning her first Grand Slam at the French Open in June, but all that is under threat. Battling a bad back and a four-game losing streak, Halep of Romania is racing to heal in time for the WTA Finals in Singapore, Oct. 21-28, to defend her No. 1 ranking. This conversation has been edited and condensed.

This has been a big year for you.

It’s been the best year in my career, winning a Grand Slam. Being No. 1 is great, but it is even better to win a Grand Slam. The Australian Open was also a great experience for me. I pushed my limits and saw that everything was possible. I saw that I’m strong and can push myself very hard. I think that tournament helped me believe that I can win one of the biggest tournaments. At the beginning of the year, after Melbourne, I just felt I was really able to win a Grand Slam.

Consistent play has been one of your defining characteristics this year. How have you managed to maintain that level of play?

I’ve enjoyed it more this year. I haven’t been putting negative pressure on myself. If you do that, you can’t handle anything. I’ve been through that before coming in the top. But with experience and tough moments, I learned that if you enjoy it more, and take every tough moment and tournament that you have to defend as a challenge, it’s much better.