You're being very kind there, Kev, absolutely, unequivocally negligent.
Even if we give the benefit of the doubt and say Richardson was the only person in the industry who hadn't heard the rumours of Yarran's personal issues, what was in plain sight was the facts that he was a selfish person who sulked when he didn't like his role in the team, had no capacity to deal with any defensive pressure and would give up when it was applied, and was a poor trainer with non-elite standards and fitness levels.
That was all obvious to even a passing observer of his football, how a GM of football wanting to trade for him either didn't see it or ignored it was inexplicable.
Even if Yarran had been healthy and ready to play it would have been an incredibly bad deal.