Even if he's not a big name yet, he didn't come from nowhere. Chacin led the Minor Leagues with 18 wins last year, and he added one more in the postseason and another as a September callup.
The Jays decided to keep him in the rotation during this year's Spring Training, a move that pushed Miguel Batista into the bullpen.
So far, Chacin's made that move look like a no-brainer. He's thrown at least five innings in each of his starts, and he's only allowed more than three runs on one occasion. He's been Toronto's best pitcher -- with all due respect to Roy Halladay.
Chacin ranks second among AL starters in wins and third in ERA (2.48). He also leads all rookies in wins, innings pitched (32 2/3) and opponent's batting average (.222). The last Toronto rookie to win four games in a month was Juan Guzman in September of 1991.
So where did all this success come from? Is he surprised to perform this well right out of the chute?
"It's not routine. You've got to work hard for this," said Chacin of his early success. "It's a little bit surprising, but if you work hard every day, this is going to happen to you. If you work hard and pay attention to everything, it happens to you."
The Venezuela native is just the fourth Blue Jay to win the designation since the award's inception in 2001. His chief competition for the award came from three position players: Chicago's Tadahito Iguchi, Tampa Bay's Jonny Gomes and Oakland's Nick Swisher.
Blue Jays catcher Gregg Zaun is particularly impressed with Chacin. After catching the rookie's eight-inning shutout against Texas, he cautioned people against underestimating him.
"I don't think it's a flash in the pan. I think he's very good, and I think he's going to continue to get better, as long as he keeps working," said Zaun. "And he's not the kind of kid who's going to take a whole lot for granted and lose track of what he's doing or where he is.
"He goes about his business very professionally, and I think he has the desire to get better and better."