We know nothing about Diedhiou. we don't know if he will ever be a Gopher or not. I would have rather had a guy who is ready to play ASAP than waiting around to see what happens with Gaston.
AI - if that's the guy you are thinking about - has an ASAP date of next Fall. Gaston assuming he qualifies and I bet he does (he's paying $11,000 + for the chance to) is ready to play in January, which is a sooner ASAP date. For now we know that, this coaching staff, who I trust on recruiting, chose Gaston.