Serena Williams' doubles campaign at Queen's Club could be over after just one match.
Victoria Mboko, the American star's doubles partner, retired from her singles match against Karolina Pliskova on Wednesday after sustaining a knee injury in the second set.
Williams and Mboko won their opening doubles match on Tuesday - in 44-year-old Williams' return to professional tennis after nearly four years away from the sport - and are scheduled to play again on Thursday.
