P Gustavo Chacin
Signed as an international free agent out of Venezuela back in 1998, Chacin arrived on the MLB scene during the time when the Jays have been desperately looking for the ideal complementary rotation piece to support team ace Roy Halladay. Chacin made the most of it when he finally got the chance to start full-time for the ballclub in 2005 alongside Halladay, Josh Towers, Dave Bush and Ted Lilly. Just looking at the rotation like that, everyone knew it needed as much help it could get.
For the 2005 season, Chacin did his part by putting together an impressive rookie season in which he went 13-9 with a solid 3.79 ERA, 1.39 WHIP, along with 121 strikeouts in 203 innings pitched in 34 starts. Those solid stats put him second on the team behind just Halladay while finishing a respectable fifth in the AL Rookie of the Year voting that season in the process.
However, he failed to sustain that success in the following two seasons. Not only was he unable to maintain an ERA below 5, he was constantly being plagued by the long ball by giving up close to two home runs per nine innings pitched. As a result, Chacin eventually found himself back in minors and was never able to regain his starting status with the ballclub. He left the organization following the 2008 season and came back as a fully reinvented reliever with the Houston Astros in 2010. But he failed to impress once again and was ultimately out of baseball following the 2011 year.