About a month ago, on the evening of January 17, things could not have been much headier for Lakers fans. Their team was 26–13 and seriously threatening the elite tier of the NBA. In fact, the Lakers had just beaten the San Antonio Spurs 100–96 in Texas, a victory that was easy to read as a statement game. It seemed that the revival of the Lakers from a 34–48 mess to one on pace for 55 wins might rank alongside the titles as among coach Phil Jackson’s great achievements.

Everything since that night has been one great big reality check. The Lakers went into last night’s action losers of 11 out of 15. The question is no longer can they challenge the best teams but how much talent, expiring contacts, and draft picks will they have to fork over to the Nets for Jason Kidd. And will that move save the season?

The reversal of fortune was easy to foresee, as are the long-term implications of the change. The conventional wisdom is that a string of injuries caught up to the Lakers, and it’s true that several players, most notably Lamar Odom, Luke Walton, and Kwame Brown have been dinged up during the nosedive, and now Vladimir Radmanovic is out for between six and eight weeks with a separated shoulder. While the team’s M*A*S*H unit is unusually busy, the real problem was a player who has been healthy throughout, point guard Smush Parker.

Although Parker’s play last week against the Knicks was horrid (3–13 shooting for nine points), his offense has been acceptable for a player who is not relied upon for his scoring (11.6 ppg on 43.5% shooting). But oh, his defense. Knicks fans most likely recall the final New York possession last Tuesday when guard Jamal Crawford changed his usual strategy of holding the ball and hoisting a rainbow and instead drove past a defender, drawing the interior defense to him, and lobbed an alley- oop pass to Eddy Curry for the gamewinning slam dunk. The Laker defender who was beaten — setting off the auspicious chain of events — was Parker.

And lately, Lakers fans might dispute the word defender. Defense isn’t Parker’s forte, and he’s been the primary offender on a Laker defense that has slipped badly from last season. Last year the Lakers finished 15th in Defensive Efficiency, points allowed per 100 possessions. This season, they’ve fallen to 22nd. Not exactly conduct becoming a team that wants to make it beyond the first round of the playoffs.

At 82games.com, an opponent’s production is tallied by position. This is the composite of opposing point guards against the Lakers: 21.3 ppg 8.4 assists per contest and 31% of opposing point guard’s shots against the Lakers are coming from in close. In other words, Crawford’s waltzing by Parker is an everyday occurrence at the Staples Center.

The Lakers’ slide hasn’t been caused by an offensive failing — they still rank in the top 10 in Offensive Efficiency — but rather a steep and worsening decline in their defense.

All this only serves to thicken the plot in which rumors of a trade involving the Nets point guard, Jason Kidd, have only multiplied. Most of the attention focuses on Kidd sharing the court with Kobe Bryant or how well Kidd might adapt to the triangle offense, which he rebelled against in Dallas in the late 1990s. But the real asset Kidd would bring to the table is defense. Every team Kidd has joined has improved — some markedly — on defense. His Hall of Fame plaque will go into great detail about his triple doubles and there will be videos of his alleyoop passes but Kidd’s primary strength is shutting down the opposing playmaker. And he keeps them out of the paint. Opposing point guards have managed only 25% of their shots from inside against Kidd and Co.

While Los Angeles has for days had an offer of rookie guard Jordan Farmar, draft picks, and expiring contracts on the table, the Nets are holding out for young center Andrew Bynum. Given the Lakers weaknesses and that the return of Walton, Brown, or Radmanovic won’t do much to help their backcourt defensive issues, the Lakers’ general manager, Mitch Kupchak, will have to think long and hard about the deal. Normally you don’t trade young bigs, but with Kobe’s window of stardom likely to close in a few years, it’s something to consider. And although Kidd turns 34 next month, guards who rebound well tend to age much more slowly than their non-boarding counterparts.

Without a trade, it’s easy to predict the future for this Lakers team. Their schedule softens a good bit down the stretch, and barring further injury, they should be able to comfortably secure a second tier seed in the Western Conference. But by early May, the Staples Center should be free of pro basketball.

mjohnson@nysun.com