"[Diaz was] the same fighter, but more prepared. The same fighter, but really ready to fight," Porter, who called the fight for Fanmio, told Babcock on the TMZ Sports TV show (airs nightly on FS1).

Shawn continued ... "They said Nate didn't really train for the fight with Jake Paul. He didn't take it as serious as he should have. And it showed."

After the fight, which Nate won by majority decision (one judge scored the fight a draw), the 39-year-old called out The Problem Child ... saying he wanted to run things back in the squared circle.

We asked Shawn -- who also worked the Paul-Diaz scrap (Jake won the August '23 10-round bout by unanimous decision) -- whether he had an interest in that rematch.

"Am I interested in seeing that fight? I think that fight might be even more exciting now. If he's taking it serious the way he took this training camp serious for Jorge, that could be an interesting fight for him in the future."

We talked to Porter about much more, including whether the judges got the outcome of the fight correct (some people think they screwed up), as well as if he thought Masvidal would be more polished in the ring (Gamebred's long been called the best boxer in MMA).

"I did [expect more out of Jorge]. I thought he was going to be sharper. I thought his punches were going to be crisper and stronger than they were. And this is what happens in the boxing ring," Porter said, explaining Nate's punching pace threw Masvidal off his game.

"I thought he was going to come to the ring ready to unload on Nate Diaz. And he never truly did that."

Turns out Shawn wasn't the only star boxer in the building to watch the fights in Anaheim ... the much-maligned Ryan Garcia, whose brother Sean was on the card, was also in attendance.

25-year-old Garcia has been under serious fire since using a racial slur on social media last week. Ryan later apologized, explaining he was "under the influence," and vowing to check into rehab.

Shawn has known Ryan for years ... and we asked for his take on the situation.