Willis has dealt with multiple injuries over the past couple of years, but this would come as a surprised since he is only 30 years old.
We will have to see if this is the big announcement that has been rumored this morning. It would be another big blow to a 49ers franchise that seems to be in disarray.
Source: the #49ers are bracing themselves for the loss of LB Patrick Willis. Expecting him to retire.
— Rand Getlin (@Rand_Getlin) March 9, 2015