Complex sentence: His position is that unless a player is guaranteed to be selected in the first or second rounds, they should not physically attend the draft, reasoning that some players could be disappointed if they are drafted later than expected, or worse, not at all.
Split into simpler sentences: His position is that unless a player is guaranteed to be selected in the first or second rounds, they should not physically attend the draft. The reason for this is that some players would be too disappointed if they are drafted later than expected, or worse, not at all.