Joel Embiid said the Philadelphia 76ers are "playing scared" after suffering a second consecutive home loss in the NBA.
Championship hopefuls the 76ers had opened the season with a flawless 14-0 record at Wells Fargo Center in Philadelphia.
But the 76ers (20-10) have dropped back-to-back games on home court, upstaged 117-98 by the Dallas Mavericks on Friday following Wednesday's defeat to the Miami Heat.
The 76ers – who have lost three straight games overall – have looked uncomfortable and a shadow of the team attempting to reach the NBA Finals.
All-Star Embiid, who led the 76ers with 33 points and 17 rebounds, told reporters: "I feel like, especially tonight, we were playing scared. Basketball is easy. You just shoot it, pass it, move it. If you don't got a shot just pass it.
"I felt like tonight we had a few open looks, [and] you just got to shoot it. But then again, it's also a balance, that's what I've been dealing with. You got a lot of people telling you to be aggressive and all that, and obviously you don't want to be selfish, but at the end of the day if you got to make something happen, you got to, especially if you feel like you have a look.
"In those situations if you're wide open, or if you're open, just shoot it. We're going to get an offensive rebound or we're going to make something happen."
Like they did against the Heat midweek, the 76ers struggled against zone defence as Philadelphia fell to sixth in the Eastern Conference standings.
"I think that the influence that our inability lately, to, like, be put on our back heels against the zone has crept into our defense, our psyche, our spirit," head coach Brown said. "And I can't stand it.
"This is not who we are. It's not who we are. ... I love coaching these guys, because I respect them. And I feel like our competitive spirit has taken a dent because of our inability to score, and I think that any time you get into a mood swing that affects your defense because your offense is doing something, it needs to be addressed."
Brown added: "I haven't seen that in this group ... how long has it been since the Brooklyn game? Six days? Before that, we were all feeling pretty good ... the past six days, if that's what it is, the past three games we have laid eggs. We have not played with a competitive drive that reflects this team. It's not, at all, how I see the world."