Blackmon recently returned from a four-match ban for his second violation of the NFL's substance-abuse policy in the last year, while his chequered past also includes two arrests in the last three years.
However, while the 23-year-old may have something of a reputation amongst the public, Henne insists that he has taken major strides in his life and has become a "tremendous" person.
"Everybody sees all the off-the-field issues and all we see is him working hard, getting better as a player and as a person," Henne told reporters.
"He's just a tremendous guy. I respect what he's gone through and how he's handled it. He's really come a long way."
The Jaguars are currently bottom of the AFC South having failed to win any of their opening six matches.