So in Season 3, when basketball season starts again, Lucas is out of shape, constantly out of breath, and lagging behind the rest of the team, he takes responsibility for it and tells Whitey not to blame everyone else for his condition. Of course, Whitey responds by pushing the entire team even harder in practice.
Now, I know Nathan was angry at Lucas at the time because of the whole Dan situation and because Lucas went to see Haley after Nathan specifically asked him not to. Personally, I always found that entire conflict ridiculous. It felt like the writers were trying to reset them back to Season 1 for drama's sake.
But even with all of that going on, I feel like Nathan should have noticed something was off. Lucas wasn't just rusty, he was struggling physically.
I always thought Nathan should have been the first person to ask: "Hey, man, about that HCM test... are you sure you don't have it? What's going on?"
It's strange to me that Nathan never once seemed to consider the possibility that Lucas had lied about the results. Instead, everyone just accepted that Lucas was out of shape and moved on. Looking back, it feels like a pretty obvious conclusion that nobody even thought to explore.