When they returned from their Mexico City trip and beat Eastern Conference playoff contender Washington to climb within four wins of .500, the Nets ranked as one of the surprises of the NBA season. But four straight losses have dampened that enthusiasm and put the Nets and coach Kenny Atkinson into soul-searching mode.

In each of those four losses, the Nets (11-19) dug themselves a double-digit hole by an average 13.5 points in the first half, and they never recovered. Atkinson admitted he must consider changing the starting lineup before the Nets face the Wizards, who were without point guard John Wall in their last meeting but will have him back Friday night at Barclays Center.

“I think four losses in a row, we have to look at everything,” Atkinson said after the Nets lost to lowly Sacramento after trailing by 21 points in the second quarter. “We have to look at what our lineup looks like to start. We have to analyze it and see if there is something to change up . . . We’re going to have some long film sessions coming up. I can guarantee you that.”

The Nets rallied within two points of the Kings in the final minute Wednesday night and allowed only 40 second-half points, the third-fewest they have given up in any half this season. But the problem was a first half that ended with them trailing 64-48.

“I don’t know what you want to call it — lack of focus, lack of attention to detail, lack of effort — but 64 points in the first half is inexcusable,” point guard Spencer Dinwiddie said. “I think it’s on the players, especially the first unit.

“We have to come out and be better, and we have to get stops to set the tone for the game. If we don’t set the tone and impose our will, then the other team is going to do that to us.”

One factor in the Nets’ slow starts might be settling for three-pointers early instead of driving to the paint to score or to draw the defense and create more open threes. “If our points in the paint are down, we probably should be more aggressive,” Dinwiddie said. “We need to be aggressive in getting into the paint whether it results in a layup or a kick-out. We’re going to live with those shots because we believe in our guys.”

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Following the trade that sent backup power forward Trevor Booker, who provided rebounding and defensive energy, to Philadelphia, the Nets won two of their next three games. So no one wants to use his departure as an excuse for their defensive struggles. Veteran small forward DeMarre Carroll said it’s ultimately a matter of the Nets taking a “scrappier,” more aggressive approach from the start.

“We’ve got to come out and be more aggressive and be more physical,” Carroll said. “Until we can do that, you’re going to keep seeing the same story . . . The guys on the court, we can look each other in the mirror and hold each other accountable. Once we start doing that, we’ll start winning these games we’re supposed to win.”