Stankiewitch has a wrist injury and will revert to the team's injured reserve if he clears waivers.
Caldwell spent two days with the Jaguars in May, trying out for the team during a rookie minicamp. The 6-foot-3, 315-pound Caldwell was a third-round draft pick by Houston in 2009. He played in 39 games with 19 starts. He spent parts of the 2013 preseason with Buffalo before being released in final cuts.
The former Alabama standout was a first-team All-America selection as a senior in 2008. He was a four-year starter for the Crimson Tide, seeing action at guard and center.
Jaguars center Mike Brewster struggled in the team's preseason opener, airing two shotgun snaps over quarterback Chad Henne's head.
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