Over one striking night earlier this offseason, as the 49ers managed to secure commitments from two star offensive linemen, it was clear that coach Kyle Shanahan was intent on investing heavily in a front that’s been inconsistent at best over his four seasons at the helm.

The 49ers awarded star left tackle Trent Williams the largest contract for an offensive lineman in NFL history. Shortly thereafter, news broke that they’d reached an agreement with center Alex Mack, another All-Pro.

In one fell swoop, Shanahan had netted his scheme’s prototypical fits at possibly the offensive line’s two most important positions.

Williams — who entered the league with Washington under Shanahan and his father, Mike, as the No. 3 overall draft pick in 2010 — might still be the best outside zone-blocking left tackle in football, as he showed with the 49ers in 2020. Mack, who’s twice previously been the pivot point of Shanahan offensive lines, was the NFL’s center of the decade for the 2010s. The 49ers are counting on him to again be a difference-making fulcrum.

So far, this has been Shanahan’s boldest offseason of line investment with the 49ers, but it’s not the first time the team has spent considerable resources on its front.

In 2018, the 49ers acquired another expensive center-tackle combination, signing the since-injured Weston Richburg to a contract worth up to $47.5 million before drafting Mike McGlinchey with the No. 9 overall pick.

In 2020, after the 49ers learned that left tackle Joe Staley had decided to retire, the team considered drafting rookie tackle Tristan Wirfs at No. 13 but instead opted to trade a third-round pick for a proven veteran option in Williams, whom they signed to that record-breaking deal less than a year later.