Alvarez had his contract purchased by the Blue Jays and will make his Major League debut on Wednesday night in a start against the Athletics.
The 21-year-old made waves with an All-Star campaign at Double-A New Hampshire this season before joining fellow top prospect Brett Lawrie in Toronto.
"I'm very happy to be here in the big leagues," Alvarez said through interpreter Luis Rivera. "That was my goal for this year, pitching where I started and to finish in the big leagues. I'm glad to be here by now."
Alvarez officially joined the Blue Jays organization when he signed as a non-drafted free agent in 2006. The converted third baseman made his debut in '08 with the Gulf Coast Blue Jays and began to work his way through the club's Minor League system.
The native of Venezuela went 8-7 with a 4.33 ERA in 23 games last season for Class-A Dunedin while earning a spot at the XM Futures Game. But it was this season that he really began to catch the attention of Toronto's brass and new manager John Farrell.
Alvarez became one of the surprise story lines during camp with an upper-90s fastball and above-average changeup, and he appeared closer to the big leagues than most people originally expected.
There still was a clear need for a reliable third pitch and after a failed attempt at developing an effective curveball, he began working on a slider. That's one pitch that helped prepare him for the next step.
"His slider has come along," Farrell said when asked what the club saw in his progression this season. "It has given him a defined third pitch in addition to his fastball and his changeup.
"He has continued to show strides in his overall command and overall performance coming out of Spring Training ... We've got a young, very good looking pitching prospect. [We] felt like it was time to get his feet wet up here."
Alvarez possesses an impressive amount of control for such a young pitcher -- he walked just 17 batters in 88 innings for New Hampshire this season. Farrell attributes that to the hurler's athletic abilities, which allow him to repeat his delivery and release point on a consistent basis.
The rookie has never been much of a strikeout pitcher during his Minor League career. Last season, he struck out just 78 in 112 1/3 innings with Dunedin and this year in Double-A he struck out 66 in 15 games.
Alvarez said part of that has been by design but he also feels like the addition of a slider gives him the ability to strike guys out when needed.
"I never pitch to strike out anybody," Alvarez said. "I pitch to contact.
"I'm not thinking about strikeouts. I'm thinking about quick outs, pitch deep into games and now with the slider that's the pitch I'm going to probably increase my strikeout ratio."
Alvarez went 8-4 with a 2.86 ERA in 88 innings for the Fisher Cats this season. He threw one complete game and allowed 81 hits while making his second consecutive appearance at the Futures Game.
To make room on the 25-man active roster, the Blue Jays outrighted left-hander Wilfredo Ledezma to Triple-A Las Vegas. The native of Venezuela allowed three runs in three innings with the club this season.