Last we saw former Wizard Gilbert Arenas, in September, he was challenging former teammate Nick Young to a three-point shooting contest, showing up at the gym with a monogrammed man-purse filled with $100,000 in cash. Young didn’t show up; Agent Zero proceeded to hit 97 of 100 three-pointers anyway.

So Arenas, who last played on an NBA court in 2012 and turned 37 last month, seems to be keeping himself in at least some sort of shape, enough to play in this summer’s Big3 three-on-three competition. On Thursday, the league announced that Arenas has joined its draft pool.

Arenas informed league co-founder Ice Cube of his intention to join the league during the former’s “No Chill” podcast this week.

“Every year it comes, I always say the same thing: ‘You know what, I’m gonna train for it, and when it comes around, I’m gonna be prepared for it and bust their a--,’ ” Arenas said. And after Ice Cube gave Arenas some Big3 swag to keep the league at the forefront of his thoughts, Arenas announced that he indeed had been training since January in anticipation of joining the league.

“I think a lot of people watched the first year to try and figure out the speed of it, and when I watched it I was like, ‘Whoosh, they’re really going, they’re really playing basketball.’ So I don’t think I’m trained and prepared for that sport right there,” Arenas said of passing on the league over its first two seasons. “It’s one of those things where I need to train like I’m playing in the NBA again ’cause I’m not gonna let them get the best of me. So I got four and a half months” to get ready for this season.

Reminded by Ice Cube that he can’t just show up at the start of the season and play, Arenas made a snap decision.

“I’m just gonna say yes now,” he said.

Said a very happy Ice Cube: “That’s all I wanted to hear. . . . Oh man, that’s a beautiful thing.”

After both television audiences and ticket sales grew in its second season, this year the Big3 will expand by four teams to 12 and play on two nights per week instead of one, visiting 18 cities over the course of the season. The draft usually takes place in April, with teams filling out their six-man rosters from the players in the draft pool. Not everyone will be selected, however: Last year, there were only 19 open spots available for more than 60 players in the draft pool.

A number of other boldfaced names have signed with the Big3 in recent weeks, including Lamar Odom, Will Bynum and Steve Blake. On his podcast, Arenas said the idea came to him after a talk with Michael Jordan.

“He said, ‘You in the Big3 yet?’ ” Arenas said. “I said, ‘Nahhh.’ He said, ‘You know what, that’s a good concept.’ I said, ‘Why?’ He said: ‘Cause there’s always retired players that still want to play. That’s gonna be around for a while.’ ”

As for his preferred landing spot, Arenas said he already has teammates in mind.

“I want all my Wizards teammates that didn’t shoot the ball,” he said. “I want Etan [Thomas]. Brendan Haywood, I want DeShawn Stevenson, Kwame Brown. You know, they already know my style. . . . Eddie Jordan, where you at? We already know the plays.”

In Big3 games, the first team to 50 wins and must win by at least two points.

“We’re looking for a player who can score [all] 50,” Ice Cube told Arenas.

“I damn sure gonna try,” was the response from the former Wizard, who added: “I don’t want ‘Arenas’ on the back [of my uniform]. I want ‘Agent.’ ”

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