Former champion Maria Kirilenko retired from her first-round match at the KDB Korea Open on Wednesday due to a back injury.
The 14th-ranked Russian, seeded second in Seoul, was one game all against local wild card Lee So-Ra when she declared herself unable to continue.
"I got an injury a few days ago, and practiced, but I didn't hit or do couple of things," Kirilenko told the tournament's website. "Practice got it better, and I like this place very much, I really want to play, but in the second game 15-40, it's getting worse," the 25-year-old Russian added.
It was unclear how serious the injury was; Kirilenko said she would await the results of a checkup at a Seoul clinic before drawing any conclusions.
Kirilenko beat Sam Stosur to win the title in 2008.
Caroline Wozniacki of Denmark is the top seep for the $500,000 hard-court event.
