In a perfect world, one in which there are no salary-cap limitations and coaches can find players in the draft and free agency who fit their team's needs, Doug Collins would have a bruising 7-footer on the roster; a guy who takes charges, tries to block every shot and has a voracious appetite for rebounds.

That would allow the 76ers coach to better utilize the skills that Marreese Speights owns - a feathery jump shot that belies his size, wonderful moves near and around the basket. But the reality is that Collins needs Speights, listed at 6-10 and 245 pounds, to be that aforementioned guy, and he's not. This is why Speights' name has been coming up as player who might be traded out of Philadelphia three years after the team took him with the 16th overall pick in the 2008 draft.

"Whatever Coach asks me to do, I'm going to do," Speights said. "I'm going to do the best that I can to play defense and rebound. Anything that will get me on the court I'll feel good about it. I want to be here."

As Collins improved the Sixers by 14 wins (41-41) in his first season last year, he admits that he was at his worst in coaxing Speights into doing what the Sixers needed from him.

"As I look back on last year as a coach, my biggest failure was I don't think I got the best out of Mo' Speights," Collins said Tuesday following the morning practice at Hagen Arena on the campus of St. Joseph's University. "You know you can go to him and that he is going to come off the bench and score."

But this is not what the Sixers need him to do. For bench scoring, the formula is pretty simple. Thaddeus Young is one of the better scorers in the league coming off the bench. And the same thing can be said of guard Lou Williams. When they are on the floor together, someone has to play defense, rebound and do the dirty work.

Last season was Speights' worst as a Sixer. His scoring dropped from a career-high 8.6 points in 2009-10 to a career-low 5.4. His 11.5 minutes and 3.3 rebounds were also career lows.

If he's on the floor - or even on the team when the season begins in Portland on Dec. 26 - it will be only because he's willing to do just that.

"What I really need from that position is a guy who can come off the bench and play defensively well next to Thad," Collins said. "So for that big, I need more of a defensive presence and rebounding presence. It's one of those things for him where it's not his strength. I probably put more time and energy in Mo' Speights than in any player. And when it started shaking itself out, what I was asking him to do is not really his strength."

Power forward Elton Brand has had extensive talks with Speights. And he believes that Speights knows what he has to do if he's going to be here, which Brand says he does.

"I can't say defense is in someone's natures; it's just heart and wanting to go do it," Brand said. "I've seen him take charges from Dwight Howard and play defense. He is capable and I think he wants to do it. I talked to him because there is a lot of trade speculation. He told me he wants to be here so he knows what he has to do."

Who plays? Collins has yet to figure out specifically how he'll handle player rotation in the two preseason games.

"I don't know that you are going to play as many guys as you would normally play," Collins said of this Friday's game at Washington. "I think you are going to have to play 10 or 11 guys and try and make sure some guys get some minutes for you."

Contact staff writer John N. Mitchell at Jmitchell@philly.com, or on Twitter @jmitch65