It mostly told me things that we've rehashed, but the real eye-opening one for me was multiple execs and scouts' opinions of McCain. I don't think he succeeds as your sole initiator, but in a multiple ball-handler multiple initiator system like the spurs are trying to run, he works really really well. His fit for Detroit and Charlotte and beside any big playmaker is also really nice.
If you take peoples' criticisms of Sheppard and Castle, and take the halfway point between them, a lot of it describes McCain
Physical tools - he's not Castle, and he's as tall and as long as Sheppard, but he's big and strong. He weighed in a 203 at the combine, which is heavier than guys like Jrue Holiday, Kyle Lowry, and Fred VanVleet when they started in the league. He probably ends up around 210, which is really heavy for a 6'3" guard.
POA defense - he's not elite like Castle, but he's also way better than Sheppard. His weight probably helps a lot here, as strength is often an overlooked factor in defense - it allows you to bump guys off their spots consistently and hold up on a switch in the post.
Shooting - not quite 50+% from 3 like Sheppard, but high volume 40+% coming off screens and pin downs, quick release; way way better than Castle obviously
Advanced stats - Castle's are bad offensively especially against top 50 and top 100 compe ion; Sheppard's are elite. McCain is pretty good - 8.5 BPM is more than respectable for a sop re-aged freshman
College team - Sheppard was a top 2 player for an underachieving first round exit. Castle was a key starter for a dominant national champion. McCain by the end of the season was arguably the best player for an elite 8 team.
DAWG/40 - elite intangibles based on everything I've read about him; Castle is great and I've never heard anything bad about Sheppard, but McCain is definitely not worse than either of these two
Compe iveness - Sheppard had his worst game of the season and shrank in his one tournament game but had multiple good games against high compe ion; Castle played well throughout the tournament but his offensive numbers crater against any kind of decent compe ion. McCain consistently raised his game in the highest leverage situations
A few weeks ago I floated the idea of trying to get McCain and Tyler Smith with 8 and 35 through some combination of trading up and trading down if Castle was the pick at 4. In my opinion, this is still the way I would go if the spurs decide Castle is that guy. McCain provides the ball-handling necessary to serve as a dribble-pass-shoot cog, he's big enough to not get hunted easily, and he provides the elite shooting necessary as a spacer if you want to play a mediocre/bad shooter in your lineup. I am actually not sure why he is not high on Detroit's list as a trade-down candidate as his toughness, defense, and shooting pairs incredibly well with Cade, arguably even better than Sheppard.