i just summed up the cash spent for all teams.
you can already see that the 89% floor in 2018 takes up ~93% ~$2 B cap space that was estimated before.
2017 is already behind in its portion of the 89%
if 2018 does not spend the cash for the 89%, it would put even more pressure in 2019 and 2020.
you can claim that a reasonable portion could be signing bonus to be spread through 5 years.
but that means 3/5 of the signing bonus would be accounted for in the 4 year window in the salary cap.
that would reduce the amount of cap space in follow on years to meet the floor.
----------------------2017-----------------2018---------------------2019------------------2020-----------------total
cash spent ---$4,636,460,549-- $3,214,199,680-- $2,267,808,277-- $1,225,337,808-- $11,343,806,314
89% of cap-- $4,917,306,932-- $5,069,440,000-- $5,411,200,000-- $5,696,000,000-- $21,093,946,932
need to spend $280,846,383--- $1,855,240,320-- $3,143,391,723-- $4,470,662,192--$9,750,140,618