Toronto's bullpen was taxed once again after Ricky Romero couldn't make it out of the second inning, which left the club with little options but to make a move to add some depth.
"We needed some reinforcement," manager John Farrell said.
Farrell views Crawford as someone who can log one inning of relief, with Carreno capable of throwing multiple frames out of the bullpen.
Both have spent time with Toronto and in the Minor Leagues this season, most recently at Triple-A Las Vegas.
In nine appearances with the Blue Jays, Crawford has a 7.04 ERA and 1.83 WHIP, while Carreno sports a 6.60 ERA and 1.80 WHIP in six games, two of which have been starts.
The two were needed after relievers Drew Carpenter and J.A. Happ were forced to throw an extended amount of pitches in the first two games of the series. Carpenter threw 67 pitches over four innings of relief in Wednesday's loss, while Happ, who was a starter with the Astros before coming to Toronto in a 10-player deal, threw 47 over 2 1/3 innings Tuesday.
"Happ is going to need a couple days to recover," Farrell said. "Carpenter is going to be down for three days."
With the additions of Crawford and Carreno, Toronto is once again working with an eight-man bullpen.