USA's Carlin Isles might be tagged 'the world's fastest rugby player' but he wasn't quick enough to avoid a bone-jarring tackle from New Zealand's Augustine Pulu at the World Rugby Sevens Series in Sydney.

The tackle occurred in the fourth minute of New Zealand's 24-7 quarterfinal win over USA, when Isles - a former Olympic-level sprinter - accepted a pass and looked to run from inside his own 22.

The 26-year-old speedster saw Pulu lining him up in a rushing defensive line and tried to beat him on the outside, but was smashed before spilling the ball to gift New Zealand captain Tim Mikkelson an easy try.