Johnson's deal is worth about $2.28 million and includes a $62,000 signing bonus.
The 6-foot, 216-pound Johnson is the second of the team's nine draft picks to sign. Sixth-round center Luke Bowanko signed Monday.
Johnson ran 335 times for 1,765 yards and 19 touchdowns in college. He spent one season at Miami before transferring to Central Florida, where he teamed with Jaguars quarterback Blake Bortles and helped the Knights go 12-1 last season. Johnson led the American Athletic Conference with 1,139 yards rushing and 14 touchdowns in 2013.
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