Having jumped Valtteri Bottas at the start and then maintained second when the Mercedes had a slow pitstop, Vettel looked set to finish runner-up to F1 world championship rival Lewis Hamilton at Barcelona.
The world champion has looked off-colour in the past three races, and his win in Baku owed a substantial amount to luck - on form, without the chaotic final laps following the crash between the Red Bulls and subsequent safety vehicle, he would have been third there behind team-mate Valtteri Bottas and Vettel, and the Finn would have been leading the championship.
Kimi Raikkonen was forced to retire from second place on Lap 27 in the other Ferrari due to a loss of power.
Today the auto and myself, I felt that synergy which I hadn't been feeling for the whole year. While Hamilton continued to lead the Spanish GP, Bottas and Vettel switched places just before the safety auto was called with the latter now two seconds behind Hamilton.
Beating Hamilton was never on the cards but Bottas fought hard, overcoming tyre wear (on the medium compounds) to defend track position from Max Verstappen who was breathing on the tail in the final laps.
While Hamilton reported drizzle on his visor on lap 21, Bottas' pace surged, over 1.2 seconds faster than Vettel.
Verstappen's stop nine laps later unleashed Hamilton and the Briton reeled off the remaining half of the race in a controlled fashion, to triumph at the Spanish Grand Prix for a third time.
"I think as a team this weekend was flawless". Hamilton's championship lead now stands at 17 points. There is... race by race we're understanding the tires more, which is a bit battle for everyone. I think now he has put all these things behind him and had a good weekend and this is what racing drivers need. It's early to say but I hope it can be part of a turning point.
The race started in chaotic fashion as Romain Grosjean lost control of his Haas-Ferrari and while spinning and smoking his tyres, spun into the path of Renault F1's Nico Hulkenberg and Toro Rosso-Honda's Pierre Gasly. It had seemed as though the Dutchman had blown another opportunity for a strong finish when he collided with Lance Stroll just after a Virtual Safety Car period, but the damage to his front wing did not seem to seriously jeopardise his race from that point.
Lap 2/66 Romain Grosjean has heavy damage and the safety auto is out.
"I was trying to go for every sector record", he laughed. The thinner tread on the rubber Pirelli have supplied this weekend in response to the blistering during testing in Barcelona certainly seemed to work to their advantage and the same type of tyres will be used at the French and British grands prix.
The victory bodes well for Mercedes for the rest of the season as the performances in Barcelona - where most teams bring significant vehicle updates - usually set the tone for the rest of the races on the European portion of the calendar. Also suffering mechanical issues were Stoffel Vandoorne and Esteban Ocon for McLaren and Force India respectively.
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