FOXBORO, Mass. — New England Patriots starting linebacker Jamie Collins remained out of practice Thursday, and now there’s some clarification into what’s keeping him away from Gillette Stadium.

Collins is “battling a virus,” NFL Media’s Ian Rapoport reported Thursday. Collins is “very weak” and “hasn’t been able to eat,” Rapoport said. Collins’ agent, Bus Cook, told ESPN’s Josina Anderson that Collins “(should) be well in a few days.”

Mysterious illnesses have made their way through the Patriots locker room all season. Offensive lineman Ryan Wendell missed practice for weeks with an undisclosed illness, and defensive end Rufus Johnson was placed on season-ending non-football illness/reserve last month.

Collins’ illness was added to the injury report Saturday. He was at Gillette Stadium on Sunday morning before being sent home.

Guard Tre’ Jackson (knee) and offensive tackles Sebastian Vollmer (concussion) and Marcus Cannon (toe) also didn’t practice Thursday.

The Patriots, who have an open spot on their 53-man roster, also had a new player on the field. Defensive tackle Robert Thomas was in the Patriots’ locker room, ESPN’s Mike Reiss reported Thursday. He was wearing No. 70, and it is’s understanding that he was signed to the practice squad and that another player will be promoted to the 53-man roster. That player, surprisingly, is not expected to be an offensive lineman.

Thumbnail photo via Mark J. Rebilas/USA TODAY Sports Images

Thumbnail photo via Feb 1, 2015; Glendale, AZ, USA; New England Patriots linebacker Jamie Collins (91) against the Seattle Seahawks in Super Bowl XLIX at University of Phoenix Stadium. Mandatory Credit: Mark J. Rebilas-USA TODAY Sports