The Charlotte Bobcats walked onto the practice floor at just before 10 a.m. Saturday. The last one to leave – Bismack Biyombo, working on free throws – left the court at just past 2 p.m.

What, exactly, goes on in a four-hour basketball practice?

“It was so long I have no clue what time it is. If you told me it’s 5 in the afternoon, I’d believe you. Maybe it is, for all I know,’’ said co-captain Matt Carroll.

This was easily the longest practice in the Bobcats’ eight-year history. As the guy who covered the Hornets from their outset, I’m pretty sure it’s the longest in Charlotte NBA history. New coach Mike Dunlap gave them Friday off, so he didn’t hesitate to work them to exhaustion Saturday.

“The crazy part is I don’t remember standing around one time,’’ said Carroll, a nine-season veteran. “He gets you thinking so much and you’re working so hard physically. You don’t realize it because mentally you’re trying so hard to keep up. So much is going on, you don’t realize the time that has gone by.’’

Dunlap calls this “overloading.’’

“I want them to have the mindset to stay plugged in when adversity comes to us during a game – a bad call or something like that,’’ Dunlap explained. “During practice, we’re trying to overload them – make it harder than a game. Then the game gets simple.’’

The players had been warned. They were expected to show up for training camp in “tippy-top’’ (that’s a favorite Dunlap expression) condition. Most of them did. There was a lot to correct, coming off a 7-59 season. So he’s thrown a ton at them, both mentally and physically, over the past two weeks.

“Because of the way we play, our fitness level has to be high-end,’’ Dunlap said.

“It’s a fast game, as far as decision-making. We’re trying to keep it simple, as far as passing and catching, but when there’s a turnover we ask them, ‘What were you thinking? What did you see?’ And we want a captive audience. So whatever we’re working on – free throws or layups or whatever – there’s no down time. We gotta go.’’

The typical NBA practice lasts two hours, 2 1/2 hours tops. Former Miami Heat coach Pat Riley used to run three-hour practices that were considered the league’s toughest. So this four-hour marathon, what was covered?

“Film, correctable errors, teachable moments,’’ Dunlap said. “Then we worked at things we know we can get better at quickly: passing, catching, defending the ball, situation play’’

They’ll be back on the practice court at 10 a.m. Sunday. This might have been a rare Saturday night off, but I can’t imagine any of these guys out partying. Most looked desperate for a power nap. And a massage. And gallons of Gatorade.

Five passing thoughts on the Bobcats and the NBA:

• The Bobcats averaged just 87 points last season, a ridiculously low number by NBA standards. I asked Gerald Henderson, last season’s leading scorer, if he’s concerned about similarly low offensive production this season. Henderson said he’s not for three reasons: 1. More offensive talent (addition of Ben Gordon and Ramon Sessions and Byron Mullens’ improvement). 2. Faster pace (running off turnovers, rebounds and even made baskets). 3. An emphasis on better shot selection (3s, rather than guarded twos, and a determination to drive to the rim more).

All that makes sense, but I still watched them score 87, off 40 percent shooting, Thursday against the Hornets. We’ll see.

• Former Duke star Austin Rivers looked scrawny Thursday, when matched against NBA shooting guards. There’s virtually no definition in his arms or shoulders. NBA guards have to build upper-body strength to fight through the screens NBA big men set. I’m surprised Rivers, son of Boston Celtics coach Doc Rivers, didn’t address this over the summer. He needs that strength and bulk.

• Ex-Los Angeles Lakers guard Smush Parker said some strange and unintentionally hilarious things in a recent radio interview, topped by the admission he disliked Kobe Bryant so much, he stopped passing Bryant the ball. In case anyone wonders why Parker is an ex-NBA player, not passing to Kobe might be a good place to start.

• Speaking of Bryant and the Lakers, I think he did the right thing by telling Dwight Howard to adjust to his new team, and not the other way around. Veteran Bryant, Pau Gasol, Steve Nash and Antawn Jamison have a small window to win a title together. Much as this will be Howard’s team later, this is his time to rebound, block shots and defer to his elders.

• I get it that unions are there to protect members, not to be popular with the public. But the players union fighting the NBA’s anti-flopping agenda is wrong-headed, particularly with so many players saying such measures are overdue.