Paul started fast, dominating the first round, landing several significant punches. Diaz looked better in the second, but Jake still controlled the round, as he also did in the third.

Nate had a few nice moments in the 4th, and even landed a hard punch that snapped Jake's head back. The round wasn't as clean, and that benefited Diaz.

Jake regained control in the 5th, landing a left hook to Nate's head, sending him to the canvas. Diaz quickly got up, and didn't only withstand an onslaught of punches from Paul, but actually began to move forward and mount offense.

The 5th featured the lone knockdown of the fight.

The rest of the fight was close.

Nate showed off his famous cardio in the later rounds (why he wanted a 10-round fight, as opposed to the originally scheduled 8), and proved once again it's nearly impossible to stop him.

Jake appeared gassed at times in the later rounds (he went 10 rounds in his 8th pro fight) ... but never looked seriously hurt, and was always throwing punches.

In fact, both men were active. Paul threw 491 punches ... landing 174. Diaz uncorked 392 punches, landing 143.

The fight went the full 10 rounds ... and Paul ultimately won by unanimous decision.

Jake's brother, Logan, was present for the bout even after competing at WWE's SummerSlam event in Detroit earlier in the night -- hopping on a private jet in order to make it to see his fam get the dub.

In his post-fight interview, Jake once again reiterated his $10 million MMA offer to Nate ... who seemed to indicate he was down to fight in the PFL.

Paul also made it clear he still wants to avenge his loss to Tommy Fury.