Draft and develop. It’s a big key to NFL success in the salary-cap era. Teams can fill some key positions through trades and free agency, which the Dolphins are doing in their current win-now window. But ultimately, to keep labor costs within limits, you need low-cost talent, which means young players. Roughly three weeks before the NFL draft (April 27-29), we’re reminded that three draft classes form the basis of the Dolphins’ rebuild — 2019, 2020 and 2021. It usually takes three years to fairly evaluate a draft class, so we’ll look back at the 2019 and 2020 classes, grading both the draftee right now and the organization’s ability to develop that draftee. We’ll grade those two classes even though the 2021 class — which includes wide receiver Jaylen Waddle and edge rusher Jaelan Phillips as first-round picks and safety Jevon Holland and guard Liam Eichenberg as second-round pick — is among the franchise’s best in recent memory.