Heather Watson was unable to celebrate returning to the top 50 with victory as she was beaten in the opening round of the Western & Southern Open in Cincinnati.
The British number one reached 46 in the rankings on Monday thanks to her run to the third round in Montreal last week.
She qualified comfortably in Cincinnati, but came out on the wrong side of a topsy-turvy clash with China's Zhang Shuai, losing 6-3 2-6 7-5.
At a set and 2-0 down, Watson looked in big trouble, but she reeled off six games in a row only to then drop the first three of the deciding set.
Back she came again, saving two match points before breaking Zhang when the world number 31 served for the match the first time at 5-4.
But Watson's much-improved serve was having an off day and she handed the break straight back.
This time Zhang seized her chance and Watson showed her frustration by flinging her racquet across the court.
It has nevertheless been a good couple of weeks for the Guernsey player, who will now turn her attention to preparing for the US Open, which begins on August 25.