Victoria Azarenka's injury involves again her foot, but this time it's the right one.

Defending champion Victoria Azarenka's injury on her right knee has forced her to pull out from the Western & Southern Open, leaving German Mona Barthel to fill her spot in the draw as replacement, SKY Sports reported.

According to the WTA, Victoria Azarenka has decided to pull out after practicing on Tuesday morning. She had apparently injured her knee during her first-round win at Wimbledon and had managed to compete in two tournaments after the grass-court major. She believes that her decision to withdraw is best to prime her up for the U.S. Open which begins Aug. 25.

"I started to feel a little bit better and did everything I could, but it's just not enough time for me to feel good to play a full match," the tennis pro said. "I'm going to get more treatment and get more work done and should be good for the U.S. Open."

This is not the first time that Victoria Azarenka's injury has forced her to withdraw from a game. The athlete , has been sidelined for most the year with an ailing foot that has caused her to withdraw from tournaments in Miami, Madrid, Doha and Rome.

"Unfortunately I will not be able to compete in Roland Garros this year," the two-time Australian Open champion, previously announced on her Twitter page following an injury on her left foot."Working hard on my recovery and getting back on court."

Victoria Azarenka's back-to-back injuries has so far earned her just a couple of matches in the past months, including one where she lost to American Lauren Davis in early March.

It has been reported by BBC, that her feet injuries probably stemmed during the defence of Victoria Azarenka's Australian Open title in January, where she lost to Poland's Agnieszka Radwanska in the quarter-finals