<p>The 19-year-old world number ‌nine slipped awkwardly while ‌facing Karolina Pliskova on Wednesday, forcing ‌her to retire.</p><p>After scans ⁠on ‌her left knee, she ​also pulled out of her doubles ​quarter-final alongside Serena Williams, the 23-time Grand ⁠Slam ​champion who returned to action this week after a near ‌four-year absence from the sport.</p><p>In an Instagram post on Friday, Mboko said she had injured the medial collateral ligament.</p><p>Mboko is the third player to ‌withdraw from the ​Wimbledon main draw since ‌the initial entry list was released, following American Hailey Baptiste and Britain's Sonay ⁠Kartal.</p>