The Jaguars were in need of a No. 1 running back because they allowed Maurice Jones-Drew, the franchise's second-leading rusher, to become a free agent. Gerhart, who has rushed for 1,305 yards and five touchdowns in five seasons with the Vikings, is expected to be in Jacksonville on Wednesday.
The Jaguars also re-signed cornerback Will Blackmon to a two-year deal, Caldwell said.
The 29-year-old Blackmon played in 15 games (eight starts) with the Jaguars in 2013 and finished with 40 tackles, 1 interception, 2 forced fumbles and 1 fumble recovery. He played in 43 games in his first six seasons with Green Bay and the New York Giants. He signed as a free agent with Seattle on Feb. 13, 2013, but was released on Aug. 27.
Blackmon signed a one-year contract for $715,000 with the Jaguars the next day.