CHICAGO -- Bobby Portis made his professional debut memorable simply by waving his arms up and down. It was the second half of an otherwise meaningless preseason opener against the Milwaukee Bucks, and Portis decided he was going to do some dirty work by jumping on the floor for a loose ball. After the play was over, the confident 20-year-old rose to his feet and did what few players, let alone rookies, do at any point in the preseason: He moved his arms up and down, exhorting the United Center crowd to make a little noise. The fans took notice and cheered, but it seems as if his teammates and the rest of the league is already taking notice as well.

"He's great," Bulls point guard Derrick Rose said recently. "I love his confidence. That's big for a rookie, big for any player in this league, but big for a rookie coming in the way he's coming in. I think that's just going to push our bigs to play harder, and who knows what he can become one day?"

Nobody knows what any player will turn into after five preseason games, but the early returns from Portis have been great. Among the 34 rookies who have played in at least three preseason games, Portis leads all of them by averaging 10.4 rebounds a game, according to ESPN Stats and Information research. Minnesota Timberwolves rookie Karl-Anthony Towns, the first overall pick in last summer's draft, is second with 6.8 rebounds a game.

"He's one of the true inside-outside bigs you can get. He's good on the block but he can step out and shoot the ball with range. You don't see much of that. There's very few of those guys. Kevin Love can go down on the block and get something done and step out onto the perimeter. But man, you're talking a handful of guys. Chris Bosh, there's just not many guys who have that and Bobby does." Pistons coach Stan Van Gundy

Portis' 12.2 points a game is fifth among all rookies, and his 1.0 blocks a game is good for fourth in the group. Year after year when Bulls general manager Gar Forman addresses the media after the draft, the basketball lifer usually says something to the effect of how surprised he was that the organization's draft pick was still on the board when they selected. This year, it isn't just Forman who seems surprised that the Bulls were able to snag Portis with the 22nd pick in the draft.

"He was a guy we really liked heading into the draft," Detroit Pistons head coach Stan Van Gundy said. "I'm not surprised with how well he's playing. He's one of the true inside-outside bigs you can get. He's good on the block but he can step out and shoot the ball with range. You don't see much of that. There's very few of those guys. Kevin Love can go down on the block and get something done and step out onto the perimeter. But man, you're talking a handful of guys. Chris Bosh, there's just not many guys who have that, and Bobby does."

The Bulls would be thrilled if Portis turned into anything close to the players that Love and Bosh have become over time, but what has been evident since training camp began is how much of an immediate impact he has made.

"Plus my impression of him going into the draft is this is just a no-nonsense, hard-playing guy that is out there to win games," Van Gundy said. "So they got a very good one. We were a little surprised that he lasted as long as he did in the draft. And I think it worked out well for Chicago; he looks like a really good one for the future."

While Portis quickly develops a reputation within the league, he doesn't seem the least bit surprised that he has come in and performed at such a high level early on.

"Surprised?" Portis said. "No. I prepared myself for this situation. I prepared myself to be a good NBA player some day. I've always worked hard, I've always stayed composed, stayed level-headed. It's not being surprised, it's being ready for your moment. Every time coach puts me out there the only thing I try to do is play hard."

Bulls rookie Bobby Portis, right, has frequently shown his all-out style during the preseason. David Banks/USA TODAY Sports

New Bulls head coach Fred Hoiberg acknowledges that developing a rotation is going to be one of his toughest challenges, but it's hard to envision a scenario where Portis isn't given rotational minutes early in the season. He plays hard, he plays tough and he has got an attitude that the Bulls could use more of this year.

"I just think it's his energy," Hoiberg said. "Anybody that goes out and plays that hard every possession, good things generally happen and that's exactly what Bobby has done."

For his part, Portis isn't shy about the fact he's going to continue to play hard. In this preseason format where players aren't always going 100 miles an hour at all times, Portis looks like a player who always has his foot planted firmly on the gas.

"I can't see myself stop [from] playing hard," Portis said. "That's something that I've always [done] and that's play hard. If I don't play hard, I'm not myself. I have to go out there and do what I do. I can't just jog up and down the court and not get intense and try to fire the crowd up and get myself pumped up. If I don't do that, then I'm not being myself and I'm doing an injustice to my basketball team and my teammates."

That's the kind of attitude everyone in the league can appreciate, but especially a player such as 20-year veteran Kevin Garnett. At 39, the Timberwolves' big man has made a career of playing harder than most. That's why the 20-year-old Portis enjoyed some trash talk with the future Hall of Famer during a recent preseason game in Winnipeg.

"He was talking about, 'Aw yeah, [this is] grown-man business right here, boy,'" Portis said, chuckling, as he recounted Garnett's words. "'I'm 40 and you 20.'"

No matter the age, if Portis keeps playing the way he has early, he'll carve out a niche for himself the way Garnett has done over time. Every possession counts -- even in the preseason.