Lewis suffered the original injury in pregame warm-ups against the New York Jets on Aug. 17 and had been limited in practice until earlier this week.
He re-injured his calf Wednesday when he tried to come off the line of scrimmage during team drills and hasn't practiced since.
Lewis, who caught 52 passes for 540 yards and four touchdowns last season, compared the newest injury to ripping a scab off a healing wound.
"I can already tell right now my calf is starting to come around a little quicker," he said. "I'm going to take it one day at a time and rehab it as much as I can and go from there.
"… The good part about it is when I felt it I pulled up and didn't try to continue to run. Maybe just scar tissue breaking up in there. I might have more access to those muscle fibers now that it's broken up."
The Jaguars will have to rely on Allen Reisner, who signed with Minnesota as an undrafted free agent out of Iowa and spent 2011 and most of the 2012 season on the Vikings' practice squad, as their top option. The Jaguars also have a pair of tight ends whom they claimed off waivers Saturday: Clay Harbor and D.J. Williams.
Harbor spent the past three seasons with Philadelphia and caught 47 passes for 421 yards and four touchdowns. Williams played in 26 games with Green Bay over the past two seasons and has nine receptions for 70 yards.