Caroline Wozniacki's clay-court campaign took another painful turn today.

The former world No. 1 retired from her Rome opener vs. Danielle Collins with a leg injury after the American won the opening set, 7-6 (5).

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Known as one of the fittest players on tour, Wozniacki retired for the second straight tournament. She retired from her Madrid opener against Alizé Cornet with a back injury, while trailing 0-3 last week.

Last fall, Wozniacki announced she had been diagnosed with rheumatoid arthritis prior to the 2018 US Open. Her ongoing health issues raise questions ahead of Roland Garros, which is Wozniacki's least successful Grand Slam. Wozniacki's best French Open result was a quarterfinal appearance in 2017.

Australian Open semifinalist Collins advanced to a second-round clash vs. two-time Grand Slam champion Garbine Muguruza.

"Obviously, I feel for Caroline, what she's going through with her injuries," said Collins. "It's never fun to go out there and play against somebody that's hurt, and dealing with that kind of pain. I was happy with the way I played, but it's just not a fun situation."

Photo credit: Mark Peterson/Corleve