The free agent guard Bears need if they keep Caleb Williams in mind

The elimination of Trey Smith as a Bears free agent option at guard will become official Tuesday at 3 p.m., barring some sort of last-second change of heart by the Kansas City Chiefs.

At that time, all tags are cemented and Smith could be considered out of reach.

This leaves the Bears scrambling for Plan B in free agency and speculation by two writers put Chicago as a landing spot for San Francisco 49ers guard Aaron Banks. First Brad Biggs of the Tribune and later ESPN's Jeremy Fowler both placed Banks on Bears radar.

This would seem like a desperation move by the Bears based on Banks' production.

There are reasons to consider a player who is ranked only as the ninth-best free agent guard according to Pro Football Focus, but the main one is lack of supply at the top of the list.

If they're not going to re-sign their own Teven Jenkins, and if Mekhi Becton remains in Philadelphia as has been rumored, it leaves them with the possibility of signing either Will Fries, Kevin Zeitler, James Daniels or Brandon Scherff.

All of these players have flaws. Fries will be expensive and his only high PFF blocking grade came last year when he played in five games before breaking his leg. He's rated PFF's second-best free agent guard and this has overrate stamped all over it because of the small sample size when he actually produced at a higher level.

Zeitler will be 35 this year and last year there were only two NFL starting offensive linemen that old, San Francisco's Trent Williams and Arizona's Kelvin Beachum. If they went with Zeitler, they'd need solid depth as insurance because 35-year-old offensive linemen tend to be injured or retire.

It's why there were two starters that old last year. Only 35, or 11%, of linemen were over 30. They'd be taking a big gamble counting Zeitler as their starter without someone else who has starting capability at the position.

Banks is lauded by PFF for his mobility in run blocking and was given a very high 15.2% run-blocking grade percentage by them. The thing about Banks' strength is that it isn't as necessary for a Bears lineman to be the most mobile blocker like it was when they leaned heavily on the wide zone scheme with Luke Getsy in Chicago or even last year. Ben Johnson said at the combine his offense relies on multiplicity of blocking schemes.

What's more important is finding blockers who can help prevent Caleb Williams from taking 68 sacks again.

Banks has never been good at pass blocking. He had a 47.3 score from PFF in true pass-blocking sets last year. He played for three seasons and has been in for only 386 more plays than Jenkins, whose basic weakness has been injuries.  Yet, he's never approached the blocking grades and production Jenkins has had as a run blocker and pass blocker. His grading has been closer or worse than Nate Davis' was.

The best Bears option if they're not bringing back Jenkins is probably Jacksonville's 33-year-old Brandon Scherff. He is older but still younger than Zeitler and very adept as a pass blocker.

Scherff last year was 19th out of 135 guards PFF graded at pass blocking and allowed no sacks with only two penalties. He was graded 53rd overall among 135. The previous year he was eighth among 136 guards at pass blocking and 45th among 136 as a run blocker.

He'd be of benefit to Williams as a pass protector possibly better than any other guard in free agency.

The cost might be more but then again perhaps not. Spotrac.com projects him at $6.7 million a year, about $2.5 million less than Zeitler.

It's an option the Bears need to closely explore when free agency begins considering what the veteran choices available.