Depends on what you want to train in this situation. I personally would want to train the SF because I hate dealing with big salaries in my rookies but the best prospect of the three would probably be the 7'1" PF because since he is a PF his secondaries are most likely fairly decent due to A+ skills and being listed as a PF instead of a Center. This way you can train him just like a center but he will naturally have better secondaries than all the other centers and will train just as fast as the other centers because he is so tall. He is the most promising player in my opinion.
Question: was that just a scenario or do you actually have these three players in your draft? :O because if so then your draft is stacked!
Murray/Harris/MPJ/Grant/Jokic - 2020 NBA Champs