It's been called a mass exodus of Biblical proportions in this corner on more than one occasion, and for good reason.

Is there a way to put a number on what the losses of five players to retirement: linebackers Patrick Willis and Chris Borland, defensive lineman Justin Smith, safety Bubba Ventrone and right tackle Anthony Davis -- at least six more key players to free agency: running back Frank Gore, left guard Mike Iupati, linebacker Dan Skuta, cornerbacks Chris Culliver and Perrish Cox and receiver Michael Crabtree, and the trade of punter Andy Lee mean to San Francisco 49ers?

Coach Jim Tomsula will have to find a way to replace 37 percent of the 49ers' snaps from 2014 to this season. AP Photo/Greg Trott

According to ESPN Stats & Information, the loss of so many players this offseason adds up to 37 percent of the 49ers' snaps from 2014, which is the highest percentage of snaps lost of any team in the NFL.

In fact, the Niners have just seven of 22 starters remaining from the team that played in the Super Bowl a mere two calendar years ago: QB Colin Kaepernick, TE Vernon Davis, left tackle Joe Staley, guard Alex Boone, and linebackers Ahmad Brooks, NaVorro Bowman and Aldon Smith.

Beyond the personnel, the Niners are also replacing coach Jim Harbaugh, offensive coordinator Greg Roman and defensive coordinator Vic Fangio with Jim Tomsula, Geep Chryst and Eric Mangini, respectively.

Chryst was promoted from quarterbacks coach while Mangini, a defensive coach at heart, served as the team's tight ends coach last season.

"Offense is a little bit out of my wheelhouse," Mangini said at the end of minicamp in June. "It had been since, I think '94, since I had coached offense, maybe '95. So I was doing everything I could to make sure I was on top of what we were doing offensively and then helping our guys look good."

The Niners looked more than good with Harbaugh, especially in his first three years in Santa Clara.

Under Harbaugh, the Niners were 44-19-1 in the regular season, the fourth-best record in the NFL during that four-year stretch, and he was the first coach to reach a conference championship in each of his first three seasons.

Call it reloading or even rebuilding, but there is a tangible way to describe the sense of loss the Niners have experienced ... even as they look forward to the challenge ahead.