Kaden Groves has missed out on the opportunity of a second win at this year's La Vuelta a Espana after the Australian ace made a fateful error of looking the wrong way amid the latest sprint denouement in Seville.

Seeking a follow-up triumph after his victory in Sunday's second stage of the Spanish grand tour, the speedster from Gympie dallied for a split second too long in the dying metres of Wednesday's fifth stage, glancing over his right shoulder for a threat which had already exploded on his inside.

For the second time in three days, his main rival for the points jersey Wout van Aert got the jump on Groves nearer the barriers - and just as in Monday's third stage, by the time the Queenslander got into full flight, it was too late.

This time, though, Belgian superstar van Aert couldn't grab the victory either, being surprisingly upstaged himself by Czech surprise packet Pavel Bittner, who sprinted to the biggest victory of his career, earning the nod on the bike throw.

Groves, who's looked the fastest man in the field, will have again been frustrated at the end of another scorching day to this time finish third after a textbook lead-out from his Alpecin-Deceuninck sprint train at the end of the 177km route from Fuente del Maestre to Seville.

It was a shock win for 21-year-old Bittner (DSM-Firmenich PostNL), who only recorded his first wins as a professional earlier this month with two stage wins at the Vuelta a Burgos.

Although Groves had earlier won an intermediate sprint from van Aert, he's now 13 points behind the Belgian in the race for the green jersey leader which is beginning to look like a two-horse race.

Three-time Vuelta champion Primoz Roglic (Red Bull-Bora Hansgrohe), victor on Tuesday's fourth stage, held on to the overall leader's red jersey, eight seconds ahead of Portugal's Joao Almeida (UAE Team Emirates) and 32 seconds clear of Spain's Enric Mas (Movistar).

Bahrain-Victorious's Jack Haig remains the leading Australian in the GC, one minute 20 seconds off the pace in 14th place.

Thursday's sixth stage sees the race return to the mountains with four categorised climbs on the 185.5km route from Jerez de la Frontera to Yunquera.