OAKLAND -- Warriors rookie Jordan Bell received his introduction to the NBA months before opening night and weeks before his first training camp.

For that, he can thank none other than LeBron James, who may or may not have been aware of being playfully dissed by Bell during a video on the night of the NBA draft.

Bell recently shared his “Welcome to the NBA” moment with NBC Sports Bay Area.

“We had an open gym in LA, at UCLA, and I was guarding him the whole time,” Bell recalled of a session last month. “It’s different than what you see on TV. It’s waaaay different.”

Bell is a 6-foot-8, 230-pound forward, James a 6-9, 260-pound specimen who defies a conventional position. Insofar as Bell is 22 and James 32, this was a crash course in Grown Man-ism.

“It’s crazy how big he is, how quick he is for his size and how smart he is,” Bell recalled. “He was standing straight up, and I’m thinking he can’t go by me if he’s standing straight up. I’m in a good defensive stance. He’s not crouching.

“But there he goes. I’m not going to say he got by me, but I didn’t realize he was so quick. For him to be standing straight up, there’s no way he should be able to move that fast. I’d understand that quickness if he got lower, but I’ve never seen anybody so quick while standing straight up.”

The University of Oregon product believes he avoided embarrassment, though he clearly was the student to James’ teacher.

“I thought I did a pretty good job on him, but he obviously hit some shots,” Bell said. “But he would get on the block, and I’m containing him, not letting him back me down, and he would fade away from the block to the 3-point line -- and make it. And I just played the best defense of my life. It didn’t matter.”

Bell did have at least one ally, Warriors teammate Draymond Green, who is acutely familiar with the futility that can come with battling with LeBron.

“Draymond was on my team,” Bell said, “and he was just like, ‘Look, you can’t do nothing about that. Just worry about the next play.’ But he also said if LeBron is taking those types of shots, that’s what we want because we’re going to make more 3s than he makes 2s.”

Bell said he left the workout trying to imagine what it must have been like to deal with James five or six years ago, when he was in his mid-20s.

“Back when he was in Miami, it looked like he was quicker than everybody else and stronger than everybody else,” Bell said of James.

Not a lot has changed, really, as James remains the single most physically imposing force in the league. Bell now knows why.

“I know they’re not all like that,” he said. “But, obviously, this is not college any more.”