The Nationals are giving up a top prospect in the 26-year-old right-hander Karns, who three made starts in his first taste of the major leagues last season, but they're adding a pair of 22-year-olds from the Jays' pool of talent: outfielder Drew Vettleson and left-handed pitcher Felipe Rivero.
Karns would have been in a crowded race for the No. 5 spot in the rotation. The trade for a younger pitcher alleviates part of that logjam and helps the Nationals stagger their pitching prospects.
To make room for the new players on the 40-man roster, Washington placed right-handed pitcher Erik Davis on the 60-day disabled list with a sprained right elbow.
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