It was the fifth stage win for Quick-Step Floors in 13 days at this year's Vuelta.
"To be honest, the finale wasn't to my taste," Trentin admitted. "On paper it looked like it was less hard, especially from three to two kilometres to go. But we decided to go for it."
"The guys were incredible. Everybody did his job and gave 100 percent. I had to win. When the team is like this, you have to finish off the work.
"It's amazing. I came in this race with confidence but I never expected something like this," said the man with six grand tour stages now notched on his palmarès.
Froome stayed safe, finishing seventh on the stage and the general classification remains intact.
It was Alexis Gougeard (AG2R), Davide Villella (Cannondale-Drapac), Thomas De Gendt (Lotto Soudal), Arnaud Courteille (FDJ) and Alessandra De Marchi (BMC) who formed the break of the day, pulling clear after six kilometres. Their advantage maxed out at five minutes after just 27 kilometres on the category three Alto de Ardales climb.
After Villella claimed the KOM points to consolidate his lead in the competition, he went back to the peloton as it slowly clawed back time on the remaining four leaders. Once the outskirts of Sevilla was reached, just De Marchi remained in the lead but was absorbed with seven kilometres to go.
Bob Jungels then set a blistering pace on the steep section for Quick-Step with just three kilometres left to race, setting it up perfectly for Julian Alaphilippe to lead-out for Trentin in the final kilometre.