Buehler, Bellinger, and Seager would seem to be the most likely candidates.
Referring to Bregman's recent extension for reference to a close comp in performance and service time, would we be willing to do 6 years / $120M for Bellinger? That would take him through is age 29 season and his first two years of free agency. Leaving this year as is so as to not affect the 2019 payroll tax numbers, and adding a $10M signing bonus, the breakdown could looks something like $11M / $13M / $15M / $17M through his four arb years and then $27M for two years of free agency.
Referring to Snell's recent extension, would we be willing to do 7 years / $73M for Buehler? Again, leaving this season out, the breakdown could be $1.5M / $2.5M for his two years of team control, then $8M / $11M / $14M through arbitration, and two $18M (with escalators/bonuses for Cy Young finishes) free agent seasons. He would end the contract during his age 30 season.
I couldn't find or think of any comp for Seager's service time. Any ideas on him?