EAST RUTHERFORD, N.J. - Brook Lopez sighed, letting out a deep breath before delving into the issues brought to light during the footage of the Nets' uneven defensive effort two days earlier.

The frequency of the schematic breakdowns and number of the wide-open looks being yielded by the Nets in Wednesday's 109-105 preseason loss to the Celtics was highlighted during a film session at practice Friday. It was another reminder of the defensive issues that have pestered the Nets throughout a preseason that wraps up after two more games, the finale coming against the Celtics in Boston on Monday.

Lopez knows it's a problem that must be corrected for a team that insists it's going to have to ride a defensive wave in order to be extremely competitive this season.

"A lot of it is effort and I take that personally," Lopez said. "I've got to do a better job on the pick-and-roll. It's something we worked on a lot last year and we got better as the season progressed. But I think with the new group, we figured some things out and I've got to be more aggressive."

It's way too early to get overly worked up given it's the preseason, particularly since the Nets are a little banged up and coach Lionel Hollins hasn't been able to get a good look at some potential regular-season floor combinations.

Still, their defense hasn't been very good and there's no denying it. There are plenty of issues that need to be addressed immediately.

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"Defensively, phew," Joe Johnson said. "We've got to do a better job of helping one another. Us as guards helping rebounding, bigs helping on the picks-and-rolls . . . Coach kind of got after us today in the film session against Boston. Playing against the Celtics, they pose a different matchup problem because they have five guys on the court who can shoot the three.

"It obviously puts our bigs in a bit of a rotation that they are accustomed to."

Take away the 1-for-5 showing by the Pistons, who aren't exactly a great perimeter shooting team, and the Nets have allowed at least 10 made three-pointers in each of their other three games. The Celtics knocked down 13 of 26 attempts.

That's why collectively the Nets know it's imperative to play much better as a defensive unit. As one of the team's leaders, Lopez is putting the onus on himself to better read certain situations.

Like being more aggressive in getting up closer to the ball-handler during pick-and-rolls, rather than simply laying off and staying closer to the paint.

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"Because when I sag back into the key, a popping big, that gives them a ton of space and it's a hard close-out to get back to," Lopez said. "So if we kill the penetration, kill the attack earlier on the pick-and-roll, it's easier to get back to those threes off the swings."

Notes & quotes: The Nets announced reserve forward Willie Reed had successful surgery to repair the ulnar collateral ligament in his right thumb and will be out for 6-8 weeks. "Definitely a tough break for him and a tough break for us," Hollins said. "But we'll move forward, he'll move forward. We had good news about the surgery. So it's part of this game, part of life . . . It just means we have less big men. We've just got to deal with what we have and go forward." . . . Rookie Rondae Hollis-Jefferson returned to practice for the first time since spraining his right ankle in last Saturday's preseason game against the 76ers. He's not sure if he'll play against the 76ers on Sunday, but was pleased to take the first step in getting back out there. "It's good," Jefferson said. "We have to play as a team, so if one man goes down it kind of messes up the chemistry. So we've got to keep everybody here as much as possible because that's our chemistry. One team, one dream and we've got to live by that. So we need everyone out there." . . . Andrea Bargnani (tight left hamstring) and Donald Sloan (sore left hamstring) were limited in practice.