Giant-killers blast way into Classic final

Jack Sock of USA plays a backhand during his semi final match against David Ferrer of Spain during day five of the 2016 ASB Classic. Photo / Getty Images.

The ASB Classic's top two seeds have fallen at the final hurdle, with David Ferrer and Jo-Wilfried Tsonga upstaged in last night's semifinals by their lesser-fancied rivals.

It was a night for the underdogs as first rising US tennis star Jack Sock toppled Ferrer, who was chasing a record fifth title in Auckland, before Spaniard Roberto Bautista Agut upset Tsonga in the later match.

Both matches were three-set thrillers in which the top seeds looked comfortable early on, before the match turned in the second set.

Today's final showdown promises to be another tightly-contested affair with Bautista Agut and Sock ranked 25th and 26th in the world respectively.

The pair have met three times previously, with the tally 2-1 in favour of Sock.

Bautista Agut eliminated the past two Auckland champions on his way to the semifinal, beating 2015 winner Jiri Vesely in the opening round, and 2014 champion John Isner 7-5, 2-6, 6-3 in the quarter-finals.

He continued that giant-killing run last night, with his consistency a proving a counterpoint for Tsonga, whose execution - particularly with his backhand - let him down. Tsonga gave up some easy points with some fairly loose backhands, which Bautista Agut exploited later in the match.

Tsonga, who quickly became a crowd favourite in Auckland this week with his post-match dances and willingness to interact with the spectators even during matches, looked to be cruising to a spot in the title decider early on.

He took out the first set 6-3 and held an early 2-0 lead in the second after breaking his opponent's first service game.

But Bautista Agut managed to get back on level pegging by breaking back in the fourth game, and from there the set stayed on serve, eventually forcing the tiebreak.

Tsonga nabbed the first point of the tiebreak with a searing ace, but from there it was virtually all one-way traffic with Bautista Agut showing impressive precision with his ground strokes to force the match to a third set.

The arm wrestle continued in the decider, with neither player able to get a break until the 10th - and what was to be final game - when Bautista Agut broke the Frenchman to take out the match.