Johnny Manziel was drafted by the San Diego Padres in the 28th round of the 2014 MLB Draft as a shortstop(1). However, Manziel is better known as a quarterback, currently of the Cleveland Browns, drafted 22nd overall in the 2014 NFL Draft, and formerly of the Texas A&M Aggies.
Given that there is a process to declare for the NFL Draft(2), What are the guidelines for declaring for the MLB Draft? What is the rationale of drafting players already established in other professional sports (eg, Russell Wilson drafted by the Rangers months before winning Super Bowl XLVIII with the Seattle Seahawks(3)).