Justine Henin-Hardenne, still in the early days of her comeback from illness and injury, is confident she can regain the form which made her world number one.
The Belgian won the Australian Open and Olympic gold medal in 2004, but a mystery virus allowed her to compete in just nine events as her ranking slipped to number 43.
A knee injury then kept her from defending her Australian Open title in January, and she only returned last month in Miami after more than six months out.
After battling to a 5-7, 6-4, 6-3 win over 10th seed Jelena Jankovic in the Family Circle Cup first round on Monday, however, the 22-year-old said she had full confidence in her ability.
"I'm sure I am going to come back," she said. "I don't know if it's going to be next week, next month, or next year but I know I will come back.
"I know what I did. I won three Grand Slams and the Olympics and no one can take that away from me, but I can't compare myself to what I was two years ago.
"But I know what I am able to do on the tennis court and I know I'm going to be able to do that in the future."
Henin-Hardenne's virus was so debilitating that for long periods she was housebound.
"Everyone knows the Justine who plays for three hours, who competes, who has a lot of energy," she said. "But I was in bed, I couldn't get up.
"It's very hard to explain unless you have been through it. The virus was a lot harder to recover from than the knee injury, because we didn't know what was happening."
Henin-Hardenne said her physical condition is improving all the time but that she is still not fully recovered.
"Sometimes I have my ups and downs, but I don't know if that's the pressure and stress of competition or the virus," she said.
"I lost a lot of confidence when I was out. Patience is probably not my best quality, but I just have to take it match by match. I will try to be patient because I need competition and I need to play.
"One of the things my coach said to me was that I can't compare myself to other players.
"I am so different from all the other players, and I am proud of that.
"I think everyone is happy to see me back but I have had to go through so many difficult things in my life and that makes my personality."