We shouldn’t. One game (or five) just isn’t enough to tell us much. The history of the summer league telling us anything about the career of a player is very spotty.
Just look back at summer league history to see this.
Randy Foye, Adam Morrison, Kyle Kuzma, Aaron Brooks and CJ McCollum have the highest scoring averages of any rookies playing at least five games in the Vegas Summer League.
Amile Jefferson, Dwight Howard, Blake Griffin, Caleb Swanigan and Mitchell Robinson are the all-time leading rookie rebounders who played five or more games.
Lonzo Ball, Brandon Jennings, Marcus Williams, Jonny Flynn and Elfrid Payton are the all-time rookie assist leaders who played five games.
Chris Clemons, Carsen Edwards, Kyle Kuzma, Gary Neal and Tyler Harvey are the all-time leading rookie 3-point shooters who played five games.
You can pick out a few really good players from those lists and a lot of players who struggled in the NBA.
The 2012 summer league MVP award was split between Damian Lillard and Josh Selby. Their careers couldn’t have gone more differently.
Bad summers don’t mean too much either. Players that struggled badly include Trae Young, Gary Harris, Eric Bledsoe, Joe Ingles and Jerami Grant, who have gone on to have really good NBA careers.
While a summer can certainly be a harbinger of things to come, it’s usually just noisy data that can’t take into account a bunch of factors which are different for each player: his teammates, his role, his skillset, his conditioning and his game readiness (some trainers forbid 5-on-5 to minimize the chance of injury).
In short, how a prospect looks in summer league should be taken with — at least — a grain of salt.