Soler, who rides for Movistar and trailed his British rival by 37 seconds ahead of the eighth and final stage in the Nice hinterland, claimed his biggest career win by just four seconds.
Briton Simon Yates moved top of the overall standings in the Paris-Nice week long race by claiming the penultimate stage, a 175-km ride from Nice to Valdeblore La Colmiane on Saturday.
Gorka Izagirre took bonus points in the first intermediate sprint of the day to jump above his brother and finish third overall, 14 seconds back.
The race victory was a first as a full pro for 24-year-old Soler, who won the Tour de l'Avenir, a mini Tour de France for under-23 riders, in 2015.
"It was a decision we planned in the morning with my team directors and my team-mates. I'm progressing step by step".
Soler did not have the legs to contest the sprint finish, with De la Cruz overhauling Fraile at the death.
A Wrinkle in Time
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Although his 11th place in the time trial may not have been against the strongest field, it did at least show that he has made some improvements in this generally weak area of his riding, but it was of course the stage win on stage seven which really stood out.
Astana Pro Team's Omar Fraile finished just behind De la Cruz, while the Paris-Nice victor finished in third.
"It was just one of those days", Yates said. The team did a really good job.
"I'm getting closer. previous year I lost Romandie on the last day as well by 20 seconds and now I lost Paris-Nice by four seconds".
After three years at Quick-Step where his talent was always evident but he never quite managed to break through, De la Cruz really seems to be relishing life at Sky, working for Henao and Poels for most of the race, before seizing an opportunity for individual success on the final stage around Nice.