Right-handers Kyle Drabek, Chad Beck and Danny Farquhar and left-hander Brad Mills will join the pitching staff, while first baseman David Cooper and outfielder Adam Loewen round out the callups.
"Given the situation with our current bullpen, we've got some guys that are banged up. We'll make no bones about it," manager John Farrell said. "There are some limitations on their physical availability, so we felt like in certain situations, we might need a couple of extra arms, and in a couple of cases, it's a reward for the year that they've had."
The four pitchers will throw out of the bullpen and have the capability of going multiple innings. That is expected to provide some much-needed depth for a young starting rotation and a relief corps that has right-handers Jon Rauch, Casey Janssen and Dustin McGowan being eased back in from various injuries.
Cooper and Loewen both enjoyed successful seasons for a strong offensive club in Triple-A Las Vegas.
The 24-year-old Cooper hit .364 with nine home runs and 96 RBIs in 120 games. He also played 13 games in Toronto this season and went 4-for-33 with one homer and five RBIs. Cooper will backup Adam Lind at first base and possibly see some time at designated hitter.
Loewen's arrival will mark another stepping stone in his remarkable comeback story. The 27-year-old was taken with the fourth overall selection in the 2002 First-Year Player Draft as a talented left-handed starter.
He pitched parts of three seasons in Baltimore, but a variety of injuries derailed his once promising career. He made the decision in 2008 to give up pitching and try to make it as a hitter.
The positive results started to come in 2011 after two long seasons in the low Minors. Loewen finished his season with Triple-A hitting .306 with 17 home runs and 85 RBIs in 134 games. He appeared at all three outfield positions and also at first base in another testament to his overall versatility.
"His swing is so much better than when we first signed him -- night and day," general manager Alex Anthopoulos said. "His approach, he can draw a walk, he's moving better in the outfield.
"It's a great success story for him to do what he did, and to get to this level, how many guys can actually do that? ... And not as a charity case, but as someone who earned it. He deserves it probably more than all of these guys."