World Cup minnows Namibia has opened the T20 tournament with a stunning 55-run upset thrashing of Sri Lanka in Geelong.

The Namibians silenced the boisterous, pro-Sri Lankan crowd with an outstanding all-round performance on Sunday at Kardinia Park.

After Jan Frylinck and JJ Smit’s seventh-wicket heroics batted them back into the match, Namibia defended its 7-163 with great bowling and fielding to dismiss Sri Lanka for 108 from 19 overs.

It puts Namibia in the box seat to progress through the qualifiers and reach the Super 12 stage of the tournament, while Sri Lanka must now beat UAE and the Netherlands in its group.

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As disciplined as Namibia was, Sri Lanka was terrible only a month after winning the Asia Cup.

Sri Lanka won the toss and looked in control, especially when off-spinner Maheesh Theekshana had David Wiese caught behind for a golden duck.

That left Namibia in major strife at 6-93 from 14.2 overs.

But Frylinck and Smit then turned the match with a big-hitting stand of 70 from 34 balls.

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Frylinck was run out on the last delivery of the innings and top scored with 44 from 28 balls, while Smit hit two sixes and two fours in his unbeaten 31 from 16 deliveries.

Namibia’s rally rolled into the start of the Sri Lankan innings, with 22-year-old fast bowler Ben Shikongo on a hat-trick in the third over.

He dismissed opener Pathum Nissanka and then Danushka Gunathilaka in his double-wicket maiden over to have Sri Lanka reeling at 3-21.

Bhanuka Rajapaksa and captain Dasun Shanaka put on 34 for the fifth wicket, before Bernard Scholtz dismissed Rajapaksa for 20 to deepen their woes at 5-74 off 10.3.

When Frylinck did for Shanaka six runs later for a top score of 29, Sri Lanka was 6-80 and there was no coming back.

Frylinck, Shikongo, Wiese and Scholtz took two wickets apiece.

Sri Lanka’s poor day started badly when promising young left-arm paceman Dilshan Madushanka was ruled out of the tournament.

The 22-year-old has a torn quad muscle and Binura Fernando, who did not play on Sunday, has taken his place in its Cup squad.

-AAP