The Sixers have had some struggles in the early days of this season, but none has been as challenging as finding an effective offense when Ben Simmons and Markelle Fultz share the floor.

Simmons is not a shooter, and Fultz has been hesitant and non-threatening from distance which gives opposing teams the opportunity to sag off on defense. Because of Simmons' athleticism and the amount he handles the ball, defenses are more wary of leaving him alone, but that's not been the case with Fultz.

Every team has forced the Sixers into a situation where they are essentially playing 4-on-5, because defenders feel completely comfortable ignoring Fultz off the ball from any kind of distance.

The play below is a reoccurring one for the Sixers: Fultz, at the top of the screen is all alone, wide open, and his defender only has eyes for the side of the court with Joel Embiid.

With such little attention being paid to Fultz, there are two major obstacles for the Sixers to overcome: Embiid is double-teamed on nearly every possession, and there are few — if any — passing or driving lanes in the paint for anyone else.

"It's a challenge because it comes back to some spacial issues that affect Joel," Brown said of finding ways for Fultz and Simmons to be assertive when they share the floor. "What I'm trying to do is have it all, play them a little bit together then separate them, then give one the ball, then the other person the ball."

But while Brown is trying to "have it all," the defense is collapsing into the paint.

See below: Dario Saric tries to drive but because both Simmons and Fultz's defenders are hugging the paint, there's no where for Saric to go, so he has to kick the ball back out.

Then, when Embiid does try to get into the post, he's more often than not met by a double- or triple-team. That's what happened throughout the Sixers' Monday night game against the Atlanta Hawks who are coached by former Sixers assistant Lloyd Pierce.

>> READ MORE: Lloyd Pierce returns to Philly

In the play below, the Hawks' Kent Bazemore (No. 24) is actually the man tasked with guarding Fultz, but from the beginning of this play he was so far away from Fultz that he was in the center of the paint.

On this particular occasion, Embiid played through the contact with multiple defenders to get to the free-throw line. But when this happens on the majority of the Sixers' possessions while Fultz is on the floor, Embiid has to work much harder than he should have to in order to score.

Fultz has an optimistic view on teams ignoring him: "I honestly look at it as more time for me to get set to shoot."

But when Fultz does have a wide-open shot, he usually hesitates, sometimes waiting so long that the crowd is begging for him to shoot. Through eight games, Fultz has shot 4 of 13 from three-point range. In three games did not attempt a single shot from beyond the arc.

Of the 64 lineups that have logged 25-plus minutes together heading into Thursday's games, the Sixers' starting lineup of Fultz, Simmons, Embiid, Saric and Robert Covington ranks 62nd in point-differential with minus-29.6 points.

For comparison, the Sixers' second-half starting lineup, with JJ Redick starting in place of Fultz (the unit that was so successful for the team last season), ranks 13th with plus-16.2 points.

The concept behind the more successful lineup is simple: with Redick demanding attention from the defense, the floor is spaced and there is more room for someone to cut and drive and Embiid doesn't have to work as hard for his buckets.

It's not a coincidence that on multiple occasions after Fultz is subbed out of the game, the Sixers' first possession has been an open lane for Simmons.

Below is the first possession after Fultz subbed out in the Sixers' home opener against the Bulls. Simmons passes out to Amir Johnson and cuts around two defenders who, caught by a screening Redick, are unable to keep up with the slashing Simmons.

It happened after Brown substituted Fultz on Monday against Atlanta and earlier in the season against Orlando:

There is, very simply, more space and more opportunity for the team to move, cut, drive and score when the defense can't ignore two players.

Fultz still has the same problems when he is on the floor without Simmons — but only when he doesn't have the ball in his hands. Defenses know Fultz is crafty and can get to the rim so they aren't going to give up on him when he is driving.

Fultz can't take all the blame. Simmons will eventually need to develop a reliable jumper, but he has the skills and athleticism that are valuable elsewhere on the court. He's also an elite and switchable defender.

Fultz, on the other hand, has struggled defensively and struggled with finishing at the rim in the early days of this season.

So the lack of an outside shot and the lack of respect from the defense is a problem that is only overcome when Simmons and Fultz are not on the court together.