Reigning Wimbledon champion Serena Williams has withdrawn from the Swedish Open in Bastad with an elbow injury.
Williams, who beat Ysaline Bonaventure in the first round, was forced to pull out of the clay-court event on Thursday, five days after her Wimbledon win over Spain's Garbine Muguruza.
"I was having some pain in my right elbow," the 33-year-old American said.
"I felt it a little bit in my match [on Wednesday], and this morning I really couldn't hit serves."
Williams, who was set to play Czech Klara Koukalova in the second round, won her sixth Wimbledon title last Sunday, completing the 'Serena Slam' of holding all four Grand Slam titles.
It was her 21st major win, and having already won the Australian and French Opens this year, she can complete a calendar Grand Slam with victory at the US Open in Flushing Meadows, starting on 31 August.
Williams added: "The main thing is that we don't want [the injury] to get worse, we obviously want it to heal."