Brussels, Belgium, 17 May 2011 | AP

Australia’s Casey Dellacqua has posted her first victory over a top 20 player with an upset win over fifth-seeded Shahar Peer of Israel at the Brussels Open.

Dellacqua fought off 11 of 13 break points she faced in her 6-1 5-7 6-3 first-round win.

After fighting back to take the second set, world No.20 Peer only managed to win half the points on serve in the other two sets and was unable to consolidate nearly any of the break opportunities she created.

Dellacqua, who has slipped to No.429 in the rankings after being sidelined with a shoulder injury, received a wildcard into the French Open starting on Sunday.

Also on the first day of the final claycourt tune-up event ahead of Roland Garros, Klara Zakopalova of the Czech Republic edged Ksenia Pervak of Russia 7-5 3-6 6-4.

Sweden’s Sofia Arvidsson beat American CoCo Vandeweghe in straight sets 6-3 7-6 (7-4) while another American, Varvara Lepchenko, beat home favourite An-Sophie Mestach of Belgium, 6-3 7-6 (7-3).

World No.1 Caroline Wozniacki has a bye in the first round.