Cal didn't play Diallo, let him be a "mystery", and look at how high Diallo went in this draft.
I don't recall Diallo being predicted to go near the top of the draft. He already had a big weakness being a guard that couldn't shoot. Not playing isn't going to show them you fixed that weakness. I believe Giles at one time was the number 1 recruit (dropped to number 2) and predicted to go number 1 in the NBA Draft without playing a game at Duke. Maybe if he sat out all year and spent the whole year rehabbing, he might not have fallen so far in the Draft. It would have netted him a much larger pay day to put away for when his knees likely give out.