This is one of those reports that, if accurate, will still be hard to believe even weeks after its initial development.

According to Rand Getlin of Yahoo! Sports, San Francisco 49ers star inside linebacker Patrick Willis is expected to retire from the NFL.

Wow.

The 30-year-old Willis has long been one of the best, if not the outright best, inside linebackers in the NFL since entering the league via the first-round of the 2007 NFL Draft.

He missed nine games - and the Pro Bowl for the first time in his career - this past season after suffering a toe injury which required surgery.

The season prior, he appeared in 14 games despite a plethora of injuries including a fractured hand.

It's fair to wonder if the mounting injury concerns are pushing the stud 'backer toward the exit.

Willis, named first-team All-Pro after his rookie season, was incredibly durable to start his NFL career, appearing in all 16 games from 2007 to 2009. Since 2010, he has appeared in all 16 regular season games just once.

He finished with over 100 tackles every year of his NFL career other than 2011 and this past season.

He has been a key cog on the recently dominant Niners teams that annually vied for the NFC West, and NFC, crowns.

With Navorro Bowman and last season's surprise, Chris Borland, already in the fold, Willis' exit will hurt from a leadership standpoint, but won't be devastating in terms of on-field production for San Francisco.

Willis, in 112 games for the Niners, has amassed 950 tackles, 20.5 sacks, eight interceptions and 16 forced fumbles.