The team also confirmed that Gronkowski suffered a "bone bruise/sprain of his right knee" in Sunday's loss at Denver.
The Herald had reported Monday that the recovery time for Gronkowski's injury was 1-2 weeks. ESPN reported he would miss "multiple weeks."
That the Patriots issued their statement in conjunction with Gronkowski's family indicates the two sides are working together.
For owners, this sounds more scary than it actually may be. The Pats aren't in any hurry to go into details about Gronk's injury and how long he'll be out. He seems unlikely to play this week against the Eagles, but we may have a better indication when the injury report comes out on Wednesday.