The Dallas Mavericks PG talked to the press Friday night after the team's loss to the Charlotte Hornets -- which actually spurred boos from the home crowd ... amounting to a somewhat ugly scene in American Airlines Center. HC Jason Kidd said it was deserved.

There's a lot of criticism about the Mavs' lack of effort in this game ... especially from their two big stars -- Luka and Kyrie -- who haven't been gelling that well since KI came on.

When asked if this is as frustrated as he's been, Luka answered candidly ... saying yes, and then going on to explain that he feels like his attitude toward the game has changed of late -- namely, he's simply not as excited to play and has effectively lost his love of basketball.

Reporters asked him to elaborate -- as that sounds like a clear reference to Kyrie, as he appears to be the one big change in the Mavs organization lately -- and Luka pivoted.

He said he was dealing with stuff off the court, and suggested that's what's causing the issues in his game. The Internet, however, wasn't buying that ... and jumped to the conclusion Luka was, in fact, expressing thinly-veiled frustration about his new teammate.

Kyrie also spoke to the media and was defiant when asked about the fans booing ... saying they're more than welcome to come on down and play if they think they're up for it.

Eventually, he talked about the transition to the Mavs and how bumpy it's been -- the team is currently out of playoff contention -- and he also said it's been rough getting adjusted.

KI was quoted as saying ... "[W]e're still feeling each other out in a way of getting used to each other's efforts and attitudes and temperament. And that's a real thing. That's a human thing. That's a human element. Whether people believe it in basketball or not, there's a very fine line between winning basketball games and everyone being on the same page and losing basketball games and things splintering and pointing fingers."