Serena Williams suffered a shock straight-sets loss to Karolina Pliskova in the US Open semi-finals on Thursday.
Williams loses the number one ranking to Angelique Kerber after the 6-2 7-6 (7-5) defeat at the hands of Pliskova at Arthur Ashe Stadium.
It also ended the American's bid for a 23rd grand-slam title and seventh at Flushing Meadows.
Pliskova, who had never previously been beyond the third round of a major, controlled the match with her big serve as she moved into a final against either Kerber or Caroline Wozniacki.
The Czech 10th seed became just the third player to beat both Williams sisters at the same US Open, joining Kim Clijsters (2009) and Justine Henin (2007).
Pliskova broke in the third game as good depth led to Williams sending a backhand long.
After a tough hold, Pliskova broke to love for a 5-2 lead, this time Williams netting with a forehand, and she had no trouble closing out the first set.
Williams needed to save a break point to start the second as she tried to get herself going before Pliskova went 3-2 up, but she gave that advantage up with a poor game.
Both players held through to a tie-break, where Williams' errors saw her fall behind 3-0 - only to win the next four points.
A double fault allowed Pliskova a way back in before Williams powered a backhand winner down the line.
Williams sent a backhand long to gift Pliskova match point before a double fault saw her bow out, giving up the top ranking.
Pliskova  bt Williams  6-2 7-6 (7-5)
Pliskova - 19/25
Williams - 20/31
Pliskova - 7
Williams - 5
BREAK POINTS WON
Pliskova - 3/6
Williams - 1/1
FIRST SERVE PERCENTAGE
Pliskova - 56
Williams - 53
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Pliskova - 84/38
Williams - 66/52
Pliskova - 69
Williams - 63