Toronto needed another outfielder after Danny Valencia sprained an ankle when he stepped awkwardly while climbing the stairs to the clubhouse following Monday's win over the Yankees. Colabello started in left field against New York on Tuesday, batting seventh.
Colabello was batting .337 with five home runs and 18 RBIs at Buffalo. A first baseman and outfielder, he played for Minnesota in 2013 and 2014.
Diaz, who was selected from Buffalo on April 28, appeared in four games with Toronto and went hitless in five at bats with one RBI.
With shortstop Jose Reyes (left ribs) on the disabled list, the move leaves the Blue Jays without a backup middle infielder behind shortstop Ryan Goins and second baseman Devon Travis. Manager John Gibbons said third baseman Josh Donaldson would move to shortstop in an emergency Tuesday, while catcher Russell Martin would handle third base.
To make room for Colabello, left-hander Jayson Aquino was designated for assignment.