That 138 is a fake number. He won’t play year 3 on that deal.
You think they're going to take an $18 million dead money hit from the signing bonus and cut him before Year 3? I'm guessing there is guaranteed salary for Year 3 as well. I don't see how he doesn't play at least four years on that deal just with the signing bonus alone.
I mean, maybe he plays 3 but not 4. I bet he restructures after 2. Guaranteed money was only 55.
Taking a stab at the yearly numbers, I came up with this:
Signing Bonus: $30 million (guaranteed)
Year 1: $1 million (guaranteed)
Year 2: $14 million (guaranteed)
Year 3: $19 million ($10 million guaranteed)
Year 4: $22 million
Year 5: $26 million
Year 6: $26 million
Why would he restructure after Year 2? The 49ers have no leverage. They're not going to cut him and take a $28 million cap hit to let him walk. They would have to give him a lot more money to restructure the contract or convert a lot to a signing bonus. If they convert to a signing bonus, that only increases the likelihood he plays on the contract in Year 4 and Year 5.
I doubt the 49ers would cut him before Year 4 as well. They'd have to take a $12 million hit and find a new left tackle. I don't think Williams would care that much if he got cut. He would most likely get a nice payday somewhere else. Given that, I count $86 million as very likely due to avoidance of dead money. That's one reason players like signing bonuses. It gives them some insurance against getting cut when the salary goes up.
He could maybe do a restructure before Year 4, but that is only going to result in him getting more guaranteed money as a signing bonus or guaranteed money for Year 5 and Year 6.
I do think it is likely that he would be cut or have to restructure after Year 4. However, that means he would have earned $86 million and then is going to get some more guaranteed money with a restructure or will get paid by another team. He might get $10-$15 million per year from another team for 2-3 years, but that would lead to him being paid over $100 million in six years.