The 22-year old former Wake Forest University star, who was taken in the 2014 MLS SuperDraft, started in defensive midfield in place of the suspended Jose Mari in the home clash with reigning champions Sporting Kansas City.
With the game just over an hour old, the Rapids were forced to shuffle their line-up when left-back Marc Burch was injured, prompting Mastroeni to send debutant Watts to a position he had never been previously deployed in.
Despite ten-man Colorado losing the game 3-2, Mastroeni admitted he was delighted with the way Watts held himself in his first appearance in North America's top flight.
"He's one of my favorites," Mastroeni said of Watts after the game.
"I ask the guy if he could slide into left-back. We have no left-footed guy on the bench at the moment. And he said 'absolutely'. And I think this guy's going to be around many, many years. He's so versatile.
"He brings a lot of heart and passion to every game, every practice. I was really pleased with his performance."
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