"We were not intending to move [Snider]," Pirates' GM Neal Huntington said. "We felt like he was a really good fit on our club."
Snider batted .264 with 13 home runs and a career-high 38 RBI over 140 games for the Pirates last season.
The 26-year-old owns a career average of .246 with 50 home runs and 184 RBI in 543 games across seven seasons with the Pirates and Blue Jays.
Huntington indicated that Gregory Polanco is penciled in as the starting right fielder this season. With Andrew Lambo, Corey Hart, Josh Harrison, Jose Tabata and others providing outfield depth, Snider became expendable.
Tarpley, a third-round pick of Baltimore in the 2013 MLB Draft, was 3-5 with a 3.68 ERA at Class-A Aberdeen last season.
“There are some things to like here,” Huntington said. “We like the upside.”
To make room for Snider on the 40-man roster, Baltimore designated catcher Michael Ohlman for assignment.