I know it’s tough to knock a team that’s won 15 of its last 16 games, especially when the one defeat came as the result of an incredible individual performance. But indulge me for a moment while I see the New Jersey Nets’ glass as half-empty.

While Nets fans are understandably exuberant over the team’s recent play, there remain some underlying concerns about how far this team can get in the postseason. We know that whomever the Nets play in the first round will be overmatched, but that’s more of a testament to the mediocrity of the East than anything the Nets have done. No, the real question is how New Jersey will fare against Miami in the second round, and if it survives that, against Detroit in the conference finals.

So let’s be clear – that is our new measuring stick. Beating out Philadelphia for the division title is nice and all, but let’s face it, when this season began and the Nets were writing their goals on the blackboard, “edging out the Sixers for a playoff spot” wasn’t on the list.

With that in mind, the last few games have raised some concerns that could manifest themselves in the postseason. First and foremost, there’s the defense. Defense keyed the Nets’ 14-game winning streak, and by the end of it they had streaked into the no. 3 overall ranking in the league.

But the effort level hasn’t been as consistent the past few games. On Saturday, for instance, the Nets faced a Cavaliers team that was without Zydrunas Ilgauskas, its second-best offensive player. But even without their main post threat, the Cavs shot 54% in the Nets’ arena. And as great as LeBron James is, the fact is New Jersey failed to contain the other Cavs as well. Cleveland players not named “James” shot 26-for-44 for an unacceptable 59.1%.

That came on the heels of two other unimpressive performances. The Nets allowed 102 points to Charlotte on Thursday and 94 to Atlanta on Tuesday, efforts that look worse once you consider New Jersey was at home and had a day of rest before each game. Indeed, after the Charlotte game Jason Kidd pointed out that, “We can’t play the way that we have these last two games if we’re going to have any chance to win” against the league’s better teams. That was borne out on Saturday, when the Nets were burned by a shorthanded Cleveland team.

You could say the Cavs game was an aberration because New Jersey’s defensive rock, center Jason Collins, fouled out in 11 minutes (or so they said – a couple of the calls against “Twin” were extremely questionable). But even with Collins in the lineup in the previous two games, the Nets faltered defensively. They’ll need to regain the intensity of the first 12 games of that winning streak – when only one opponent scored more than 89 points – if they’re going to hang with the likes of Miami and Detroit in the playoffs.

To the Nets’ credit, they took the Bucks to the woodshed yesterday, holding Milwaukee to 12 first-quarter points in a one-sided road win over their probable first-round playoff opponent. Certainly, they can dial up the intensity when the mood strikes, but they need to do for seven straight games come May.

Even if New Jersey overcomes that hurdle, however, there’s another lingering doubt left by the Cleveland game, and it has to do with Vince Carter. For years the lingering criticism of Carter is that when the going gets tough, he tries to take the easy way out – settling for jumpers instead of going to the basket and playing passively when he has the talent to dominate. That hasn’t been as big a problem in New Jersey as it was in Toronto, probably because Kidd and coach Lawrence Frank have their foot in his rear whenever he slacks off, but that shred of doubt still hangs in the air.

So it was disconcerting to see Carter settling for poor shots down the stretch against Cleveland on Saturday. With the score tied at 101 in the final minute, he twice settled for contested jumpers from 15 feet that didn’t find the net. Worse yet, he hoisted the shots early in the shot clock, when the Nets had opportunities to work for a much better shot. To his credit, Carter got to the line moments later on a drive to the basket, but his second attempt rattled out.

That set up what was for me a deja vu moment. Earlier this year I saw the Nets lose a 104-102 overtime game in Atlanta.Trailing by two in the final seconds, Carter caught the ball at the top of the key, took one dribble, then lofted a long, contested 3-pointer that rattled out. It was a beautiful shot to be sure, especially had it gone down. But the disconcerting part is that Carter had six seconds from when he caught the ball to make a move to the rim, and instead opted for the easy way out – and the lower-percentage play.

Lo and behold, I saw him try the same thing on Saturday. Down by two with time runnin out, the Nets had 21 seconds to work the ball into position for a 3-pointer; alternatively, they could have gone for a quick two and fouled. But Carter again opted for what seemed like the path of least resistance, taking a quick, low-percentage shot off the dribble from way out and watching it bang harmlessly off the rim, sealing the Nets’ defeat.

You can see the obvious concern here heading into the playoffs. The Nets’ bread-and-butter play in late game situations is to isolate Carter at the top of the key and let him create a shot. But if he’s going to settle for jumpers like the ones he took against Atlanta and Cleveland at the end of close playoff games, it’s hard to like New Jersey’s chances.

So despite the 14-game winning streak, there is work to be done. If you still disagree, consider this: New Jersey has had a 10-game win streak and a 14-game win streak this season … and in the other games, they’re 23-29. Obviously, consistency is a problem, and it’s most problematic in the two areas I described above. Until the Nets prove they can bring their A-game defensively every night, and until Carter demonstrates that he can be trusted not to settle for contested jumpers in late-game situations, I’m not sure the Heat and Pistons have a lot to fear this spring.

Mr. Hollinger is the author of the 2005-06 Pro Basketball Forecast. He can be reached at jhollinger@nysun.com.