The 2013 first-round pick arrived on the campus of Olivet Nazarene University around lunchtime Thursday, one day after the rest of the team reported to training camp, and told reporters he is recovering from a viral infection that is expected to sideline him through the weekend.
"I was pretty sick and run down this past weekend, but I'm feeling better," Long said before entering the ONU dining hall.
Bears general manager Phil Emery said Wednesday that Long will be re-evaluated at the beginning of next week.
Long was officially placed on the non-football injury list on Thursday.
No official timetable has been set for Long to start practicing, but right tackle Jordan Mills believes the Pro Bowl right guard will return in short order.
"He's going to be fine. He's tough," Mills said. "He hates that he wasn't here to see everybody yesterday."
The Bears ran their annual conditioning test Thursday morning, which consisted of three 300-yard shuttles.
Safety Craig Steltz (groin surgery) passed his conditioning test, but he will begin camp on the physically unable to perform (PUP) list along with fellow safety Chris Conte.