The shocks keep coming at the ASB Classic, as top seed John Isner has crashed out of the tournament.

The world No 10 has been upset by compatriot Taylor Fritz 7-6 (3) 7-6 (5) in a big serving battle.

It means that five of the eight seeds have already gone, including Isner, third seed Marco Cecchinato, 2018 Australian Open semifinalist Hyeon Chung and Canadian youngster Denis Shapovalov.

Both players have massive serves - Isner served a staggering 26 aces – but Fritz had the edge on the big points.

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The 21-year-old Fritz, who broke into the top 50 last November, is known for his poise under pressure.

He had the best record in tiebreakers of anyone on tour last year – better than Roger Federer, Rafa Nadal, Novak Djokovic – and showed again that strength under pressure again today.

Both players traded a single break in the first set, but Fritz had the edge immediately in the shortened format.

The second set was an even tighter affair – with neither player managing a break – before Isner held a strong game at 6-6.

Fritz gained a mini break at 4-1, before two consecutive aces brought Isner back into contention at 4-4.

But that was as close as the two-time Auckland champion got.

The 33-year-old saved a match point at 4-6 with a massive second serve, but Fritz sealed the result on the next point, after a Isner backhand drifted over the baseline after the longest rally of the match.