Former world number one Serena Williams says she is at the start of a "long comeback" after losing 6-3 2-6 6-3 to Czech Petra Kvitova in Cincinnati.
The second-round loss comes on the back of her heaviest career defeat, a 6-1 6-0 loss to Britain's Johanna Konta in the Silicon Valley Classic first round.
"I'm still at the very beginning," said the 23-time Grand Slam champion.
"I'm just going to continue to work hard, and hopefully I'll start winning more matches."