By the way, the Clemson player is not under a baseball contract NOW, and that is all that matters.
This is incorrect. A player does not lose his football eligibility by playing professional baseball, as long as the following guidelines are followed:
1. A player can sign a professional baseball contract with a professional team and still return to play NCAA football at any time - if his contract allows him to do so. He can receive money and benefits from a professional baseball team.
2. He can receive a scholarship to play football as long as he maintains his amateur status in football.
3. He can sign with an agent. ALL contracts and conversations with an agent must be specific to baseball.
4. He can receive money and benefits from an agent as long as (condition) No. 3 is met.
5. He cannot sign any commercial endorsement deal.
Clemson QB Kyle Parker did indeed sign a contract with the Rockies - one that allowed him to play football at Clemson this fall. Another example is NC State QB Russell Wilson, who has been playing in the Rockies organization this summer, and will play for NC State this fall.
The difference between Zach Lee and Kyle Parker, both first round picks, is that Lee took the money to not play football while he's under contract - which netted him 5.25 million dollars. And Parker left the money on the table so that the Rockies would allow him to play football at Clemson this fall - which netted him only 1.25 million, which is not a lot for a first rounder this year. Also, Parker stands to lose most of the money in his contract if he were to be injured playing football, as the signing bonus is spread out over time and conditional on him remaining healthy.
It is rare for a baseball team to allow a first round pick that they are paying above slot money to to play college football, which is why you don't see this happen more often. Also the seasons overlap by several months.
Note that both Kyle Parker and Russell Wilson were drafted by the Rockies, who seemed determined to sign their draftees this year, even if it meant allowing them to play football - as neither probably would have signed if they had tried to disallow them, even though it would have been for more money.
Hope this helps.