Kaia Kanepi pulled off a major upset on day one of the US Open with a straight-sets defeat of world number one Simona Halep.

Halep was blown away by the 33-year-old Estonian in the first match at the new Louis Armstrong Stadium, losing 6-2 6-4 on a warm Monday in New York.

The composed 44-ranked Kanepi outplayed the top seed with a mixture of power and precision to send shock waves around Flushing Meadows.

Halep was beaten by Maria Sharapova in the opening round at the final major of the year 12 months ago and, although the French Open champion showed some fight in the second set, the previously in-form Romanian was unable to avoid becoming the first top-seeded woman to lose in the first round of the tournament.

The unseeded Kanepi reached the quarter-finals of the US Open last year and will face Jil Teichmann in round two after breaking five times and hitting 26 winners in an aggressive performance to claim a huge scalp.

Kanepi took to the court with a strapped left shoulder but generated fearsome power from the start, going after the Halep first serve and breaking with a perfectly executed lob for a 2-1 lead.

The underdog went from strength to strength, unleashing rasping winners from both wings to consolidate the early break before going a double break up at 4-1 courtesy of a magnificent deep return.

Halep was flustered and found herself a set down in only 28 minutes when the flawless Kanepi held to love with a forehand winner.

A furious Halep marched off court for a new racket, which did not last long as she smashed it into the hard court to earn herself a code violation after Kanepi broke in the opening game of the second set.

A struggling Halep looked short of ideas as she went 3-0 down, but Kanepi gifted her a first break with a double fault in the next game.

The momentum was with a battling Halep when she got back on serve at 4-4 with a break to love, but unforced errors gave Kanepi the chance to serve out the match.

Kanepi stepped forward to let fly with a powerful forehand to earn two match points and only needed the one.


STATISTICAL BREAKDOWN
Kanepi beat Halep [1] 6-4 6-2

WINNERS/UNFORCED ERRORS
Kanepi –26/28
Halep – 9/9

ACES/DOUBLE FAULTS
Kanepi – 1/3
Halep – 1/0

BREAK POINTS WON
Kanepi – 5/7
Halep – 2/2

FIRST SERVE PERCENTAGE
Kanepi – 70
Halep – 66

PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Kanepi – 64/57
Halep – 66/59

TOTAL POINTS
Kanepi – 59
Halep – 47