Australian wildcards Thanasi Kokkinakis and James Duckworth have thrown the rankings guide out the window by claiming stunning first round upsets over seeds at the Brisbane International on Monday.

World No.149 Kokkinakis, 18, has set up a potential second round showdown with compatriot Bernard Tomic by downing French eighth seed Julien Benneteau 6-4 6-3.

And world No.125 Duckworth earlier blew away sixth seed Gilles Simon also of France, 6-2 6-2 in just over an hour at Pat Rafter Arena.

Kokkinakis had a hard act to follow after Duckworth thrashed former world No.6 Simon, currently ranked 104 places higher than the NSW 22-year-old.

However, the teenager shrugged off an early break to overwhelm Benneteau after the world No.25 appeared to be battling a hip complaint, prompting a seven minute first set medical time out.

Kokkinakis – who made his Davis Cup debut last year along with fellow member of the “Special Ks” Wimbledon quarter-finalist Nick Kyrgios – sealed the 74 minute match with his ninth ace.

Benneteau, 33, appeared sluggish after the time out and finished with 20 unforced errors.

Duckworth stole the early limelight on centre court in Brisbane.

Former Australian Open quarter-finalist Simon had no answer to Duckworth’s power, dropping the first four games of the match.

Duckworth sealed the first set in just 30 minutes before a shellshocked Simon tried to regroup at Pat Rafter Arena but to no avail.

Duckworth is on track for a potential quarter-final showdown with Roger Federer.

Then again, Duckworth comes from reasonable tennis stock – his grandmother, Beryl Penrose won the 1955 Australian Open singles and doubles.

Simon was the overwhelming favourite after an impressive finish to 2014, downing Australian Open champion Stan Wawrinka on the way to his second ATP Masters 1000 final in Shanghai where he fell to Federer.