Simone Velasco claimed the first victory of the season for Astana Qazaqstan, triumphing from a three-man breakaway just three seconds ahead of a chasing peloton.
In a thrilling finale, Velasco, Bob Jungels (Bora-Hansgrohe), and Jonas Gregaard (Uno-X) survived the Puerto del Garbí inside the final 30km and hung on by the skin of their teeth to sprint for the stage honours.
Velasco was comfortably the fastest, easing clear by several bike lengths as he opened up in the final 200 meters. Jungels took second place ahead of Gregaard.
They were followed just three seconds later by a heavily reduced peloton, which lost the likes of Biniam Girmay (Intermarché-Circus-Wanty) on the Garbí climb, and the frustration was evident as two Movistar riders bashed their handlebars as they crossed the line in 4th and 5th place.
Giulio Ciccone (Trek-Segafredo) retained the overall lead on a day when there were no changes to the general classification. Ciccone did at one point find himself reacting - needlessly perhaps - to a speculative Thomas Gloag (JUmbo-Visma) attack, and a puncture in the final 10km made for a stressful run-in, but he takes the yellow jersey into Saturday's crucial summit finish stage.
"I'm super super happy," said Velasco. "This is a victory especially for our masseur, who passed away a few days ago, Umberto Inselvini. This is for him and his family."
Jungels described it as a "suicide mission" to go in the breakaway on the 145km stage Betera to Sagunto, with an early climb and another one ahead of the crucial Garbí, which measured 9km at 5% but with some steep sections and topped out 28km from the line.
It was a big effort just to embark on that mission, with a lightning pace and no wiggle room in the first hour but the trio - along with Lawson Craddock (Jayco-AlUla) and Sander De Pestel (Flanders-Baloise) - managed to carve out a three-minute gap.
On the steep section of the Garbí, De Pestel fell away as Craddock attacked, taking a 25-second lead onto the descent only to be caught with 15km to go as the gradient eased. Not only caught but dropped, as cramps ruled out any hopes of stage victory.
In the bunch behind, Gloag provided some GC action with a long-range attack on the climb, which briefly drew out Ciccone, but the race leader settled in and the race favourites reeled in the young Brit just over the summit. At that point, there were 50 riders left and they trailed the breakaway trio by 1:25.
When Bahrain Victorious and Movistar combined on the lightly downhill run-in, the breakaway's hopes appeared doomed, their lead cut to 45 seconds with 10km to go and 20 seconds with 5km to go. However, roundabouts and road furniture as they came into town helped tip the balance back in their favour just enough for them to emerge into the final straight with time to sprint.
Gregaard led the way but Velasco jumped first and sailed clear. Gregaard's chain reportedly slipped, with Jungels saying he was hampered slightly, but Velasco showed them both a clean pair of heels and was full value for his fourth career victory.
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