Billy Donovan knows the difference between need and greed.

Before becoming a Hall of Fame coach, it’s easy to forget that Donovan was one of the elite point guards in the country, guiding Providence to a memorable Final Four run. He then went from being a Friar to a buyer, spending almost five months as a stockbroker on Wall Street.

Two different worlds and hard lessons taught in both.

So while he admittedly never had the talent of a Rob Dillingham, he knows a little bit about when a point guard should be a buyer and when he should be a seller.

That’s why there have already been a handful of tough love moments since Dillingham has joined the Bulls in a trade deadline deal with Minnesota. The ultra quick guard has shown an ability to use his slick ball handling and wiggle to get into the teeth of the opposing defense, but has also put bad habits on display, trying to score from impossible angles once he does.

Bad habits that can be broken? That’s the hope.

“He is going to have to learn what gets you here doesn’t keep you here and what gets you here doesn’t necessarily take you to a next step,” Donovan said after the loss to the Knicks on Sunday. “As the talent gap shrinks, you have to make adjustments and changes. He’s so explosive and so fast with the ball, probably for most of his career no one could keep him in front. He probably got to the rim whenever he wanted to, and he could use his athleticism to go finish. Now all of a sudden he can’t do that all the time.”

Not that Dillingham didn’t have a few wow moments in his 24 minutes of work, scoring eight points, grabbing four rebounds and finishing a plus-9 in plus/minus when he was out there.

Yeah, the missed breakaway dunk wasn’t a shining moment, and he did force a few shots in the paint, but he also rallied a few minutes after that botched slam, drove the paint and sprayed it out to Patrick Williams for the three-pointer.

Textbook point guard play in Donovan’s offense.

And that’s the one issue the coach is having with Dillingham right now – decision making. Just because he could dominate the opposition in high school and college with blow-bys doesn’t mean he’ll get away with it in the Association.

Maybe that’s why Minnesota gave up on the No. 8 overall pick after just 84 regular-season games.

“What he can do at an elite level is get into the lane,” Donovan continued. “He’s got to make (better) decisions when he gets there. There’s balance where you don’t want to take away a guy’s aggressiveness by yanking him. He’s really gifted and talented and has great speed. This is going to be the evolution for him as a player, because with his size (he’s listed at 6-foot-2) there are certain things he can’t do at the basket. What he can do is make everyone else around him better, and that’s what we have to work with him on without taking away the aggressiveness.”

The good thing for Dillingham is more playing time might continue coming his way.

Anfernee Simons is sidelined with an injured wrist, Jaden Ivey might miss the remainder of the season as his knee is an issue, and Josh Giddey and Tre Jones remain on strict minutes restrictions.

A suddenly crowded guard room is down to Giddey, Jones, Collin Sexton and Dillingham, and in the Knicks game Dillingham played more than all three.

If he wants to continue that trend, he needs to understand one basic lesson from his coach: “Greed is good,” but only on Wall Street.