On Dashon Goldson's inevitable departure

The San Francisco 49ers knew they could not re-sign every free agent after fielding the NFL's highest-paid defense last season.

That enabled Pro Bowl free safety Dashon Goldson to reach the market and agree to terms Wednesday with the Tampa Bay Buccaneers.

Goldson stood out for his big hits and strong tackles. Coach Jim Harbaugh suggested Goldson epitomized the type of player the 49ers would like to reward. But San Francisco appeared resigned to losing Goldson, its franchise player in 2012. The team could have kept Goldson by naming him its franchise player at a cost of $7.45 million for 2013,

"We have the most expensive defense in the league on an average per-year basis, and that is not sustainable over time," the team's chief operating officer, Parrag Marathe, said during the MIT Sloan Sports Analytics Conference two weeks ago. "Because of the cap, if every veteran on the team took a 15 percent discount on their market value, you couldn't field that team still under the cap because the difference between wholesale [draft] and retail [free agency] is so wide.

"You have to figure out which players to keep and which players to let move on and churn out. Because you have to continue to replenish the system."

Goldson, a fourth-round choice from the University of Washington in 2007, joins nose tackle Isaac Sopoaga among longtime 49ers defenders to change teams since free agency opened Tuesday. Two other longtime 49ers, Alex Smith and Delanie Walker, also departed the team this week.

The 49ers have an additional second-round choice in the 2013 draft. They have more choices overall than any team in the league. They need to use those choices to acquire lower-cost replacements for some of the veterans leaving this offseason. They addressed their defensive line Wednsesday by agreeing to terms with former Kansas City Chiefs defensive tackle Glenn Dorsey. More on that in a bit.