What’s even more demoralizing about the Celtics’ 100-97 loss to the lowly Brooklyn Nets on Saturday is the players primarily responsible for the Brooklyn victory were allowed to do what they have done for years.

There was no resistance. Brook Lopez constantly seized premium post position for easy buckets. Joe Johnson was allowed to either dribble and create space for his midrange jumper — that should be in the scoring report — or was left open for a 3-pointer.

In one sequence, Marcus Smart was a split-second late in approaching Johnson and listlessly waved his hand in vain to defend the shot. The Celtics made good players on a bad team look good, and therefore they were handed their second consecutive embarrassing defeat.

When the Celtics’ record was 18-13 with three consecutive games against the Lakers and Nets upcoming, the team assumed it would be 21-13. With arrogance, the Celtics assumed the Lakers and Nets would eventually relent and fall right in with the plan.

Except they didn’t. The opponents didn’t have as high regard for the Celtics as the Celtics had for themselves. You knew trouble was on the horizon when the Nets, a team that averages 97 points per game, scored 31 in the first quarter, 20 of those in the paint.

Opposing teams are attacking the Celtics’ middle at will and something needs to be addressed. But then again, Saturday was just as much about desire as lack of the proper personnel. Once again, the Celtics settled for 3-pointers. Once again, they were careless with the ball. And, once again, they attempted to atone for their shortcomings with a furious rally.

And, as they deserved, the rally fell short.

“We’re not really great enough to really say this is a bad team or that is a bad team,’’ Celtics swingman Evan Turner said. “Tonight, Joe Johnson is a problem. Brook Lopez goes without saying. You get the helpers chipping in, they want to battle. We shouldn’t have even been in [a rallying] predicament. We kind deserved that in regards to not treating the game right.’’

Celtics coach Brad Stevens took the typical Stevens approach: he blamed himself.

“I just need to do a better job, this is more on me,’’ he said. “We’ve had multiple times where we’re not playing to a standard we need to play to. We’ve had multiple practices where certain guys have really looked good and stood out because others haven’t, and that’s just bad coaching. I’ll get myself straightened out and I’ll work on what needs to be changed.’’

That’s a noble stance and perhaps Stevens needs to be more stringent, but the issues during this stretch are on the players. They need to play harder, with more of a sense of urgency. But it’s not that the Celtics are lacking effort, it’s that they are trying to make the home run play.

There have been countless times this season when the team has been burned by the low-percentage pass that skidded out of bounds or a player unqualified to attempt a 3-pointer takes one anyway. The Celtics are seventh in the NBA in 3-point attempts and 25th in 3-point percentage.

That’s called a disconnect. Somebody on this team needs to chill with their Stephen Curry fantasies and stop shooting 3-pointers, especially in clutch moments when a higher percentage shot is just a few dribbles away.

When the 3-pointer is falling, the Celtics are a formidable opponent. But they have to become better when that long-range shot doesn’t fall, when they have to pound the ball in the paint and get to the free throw line. They are too carefree, using too much finesse.

“We’re definitely not one of the best teams in the NBA, so I don’t get how we could possibly think it’s OK to play down to anybody,’’ Celtics guard Isaiah Thomas said. “When we don’t play hard and we’re not the aggressive team, we’re one of the worst teams in the NBA. But when we bring that aggressiveness and we’re having fun, we’re defending, we’re one of the top teams in the NBA. I think a lot of people see that.’’

Nobody in the Celtics’ locker room is intentionally playing selfishly or trying to stray from the team concept. This is a locker room with no cancers or players who opt for personal agendas over team ones, but the inconsistent playing time for many players has them trying to do too much when they receive precious minutes.

Players are looking over their shoulder while playing, waiting for the moment that their replacement is summoned. And in their short minutes, they are trying to make the big play that will keep them on the court. Stevens needs to stress that the big play won’t keep them on the court, but the right one will.

So once again the Celtics have reached a mini-crossroads. Monday’s rematch with the Nets becomes the most important game of the season, and Stevens’s adjustments over the next 24 hours will determine how soon this skid will end.

These two losses have been humbling, forcing the players and coaches to look within for the problem. All involved should find some fault in themselves and remember the embarrassment generated from the past week because the Celtics are definitely better than this.

“You’ve got to fall in love with success,’’ Thomas said. “You’ve got to fall in love with what works and don’t have an agenda for anything else.

“It’s a mind-set thing. What team do we want to be? Because when we come out and think we’re [more] talented than other teams, that’s when it backfires on us.’’

Gary Washburn can be reached at gwashburn@globe.com. Follow him on Twitter @GwashburnGlobe.