The performance is one that Dunne can be optimistic about, a win is what he wants but falling short to a golfing prodigy and beating him for three out of four days is impressive.
Greystones native Dunne picked up a cheque for €166k for his efforts.
The world number four began the day behind overnight leader Paul Dunne but a birdie-birdie start from the Spaniard saw him tied for the lead after two holes.
South African Gerry Coetzee surged 31 places through the field to finish fourth with a best round of the day 63.
"It would be the most special victory I've had so far".
Elvira hit 66 for the second day in a row, while Rahm struck seven birdies and bogied only once to match his compatriot's score for the day. I can not wait to see him follow in Seve's footsteps as a Ryder Cup competitor.
"I've ever been blessed to function as federal champion from 16 to most ages in Spain".
"They were pushing so hard and I felt that and as a golfer it is hard to deal with your emotions sometimes, and while I tried to isolate myself I could feel the emotion and used the crowd emotion".
The Irishman bounced back to birdie the next as Rahm, playing in the group ahead, narrowly missed the water off the 17th tee but pitched to four feet and saved par. "So being able to win this as a pro and do this for them and the Spanish people feels great".
Rahm's closest challenger, Nacho Elvira, was not so fortunate at the 17th when he found the hazard and his hopes of a maiden victory disappeared with a double bogey five.
Dunne, the British Masters champion, was "disappointed" to miss out on a second European Tour victory but, at the same time, expressed his delight for the victor.
He also reaches three European Tour victories quicker than any other player, having captured his third title in just 19 starts.
Spaniard Jorge Campillo and Scot Marc Warren carded closing rounds of 69 to finish at 15 under alongside Australian Brett Rumford and Swedish rookie Henric Sturehed, who picked up his first European Tour cheque.