It was only one play in one game in mid-November, but it was telling.

The Knicks had the ball in Saturday’s game against San Antonio, and the Spurs defense executed a switch that left Tony Parker guarding Quentin Richardson. Richardson correctly identified the mismatch, ran to the left block where he could overpower the smaller Parker, and waited. And waited. And waited….

Meanwhile, Stephon Marbury had the ball at the top of the key. He either didn’t see the mismatch or didn’t acknowledge it. Instead, he went one-onone against the Spurs’ Bruce Bowen — who is widely considered the league’s best one-on-one defender — and forced a 15-footer that missed.

That play illustrated one of the key failings of the Knicks. Many have commented that the players Isiah Thomas acquired are overpaid relative to their absolute value, and this is true. But the other, less discussed element, is that the pieces also fit together very badly.

This was made evident Saturday night not because the Knicks lost — very few teams leave San Antonio with a win, after all — but in the way they lost. The Knicks’ guards essentially took turns going one-on-one, with Jamal Crawford, Stephon Marbury, and Nate Robinson hoisting 38 shots between them. Meanwhile, New York had 11 assists as a team, or barely half what Jason Kidd mustered by himself against the Wizards on Sunday. And only eight of those dimes came from the backcourt trio.

You see, the Knicks’ guards are a classic example of the law of diminishing returns. Having one guard like Marbury isn’t a problem. Sure, he’ll miss an open man or a mismatch sometimes, as he did with Richardson, but he can break down defenses with his penetration and carry the offense for quarters at a time. But if all the guards are like Marbury, then it doesn’t work nearly as well.

That’s a fundamental flaw in the Knicks’ roster construction, unfortunately. Marbury, Steve Francis, Jamal Crawford, and Nate Robinson all have the exact same mentality — keep the ball in my hands until I can create something, and if I really get stuck, then maybe I’ll pass it. Having one guard like this is fine; even two can work if the minutes are divvied up so they don’t play together much.

But four? That’s a recipe for disaster. You’ve heard the maxim about good guards making their teammates better? Well, the Knicks have the opposite effect. Having four guards who do the same thing makes each of them worse, as can easily be seen in their productivity this season. And that effect is multiplied by the rest of the roster, where below-average passers reside at every position. The result is that few Knicks receive the ball in position for a wideopen shot; instead, they constantly have to create one for themselves.

This is most evident among the guards, since they’re the ones who are supposed to do the sharing, and particularly stands out when the team runs a pick-and-roll. The roll man might as well read the newspaper at the foul line once he’s done setting the screen, because he has a snowball’s chance in Hades of getting the rock.

The proof is in the pudding: The Knicks have the lowest rate of assisted baskets in the league. Only 46.0% of the Knicks’ buckets this year came with help from a teammate.

What’s more, the disease may be spreading. Richardson took note after the failed entry versus Parker, sending an obvious message on his next touch by putting his head down and going one-onone from the top of the key … and getting swatted by Tim Duncan. Richardson launched 16 shots, with only one attempt coming on his preferred catchand-shoot 3-pointer. Those shots are few and far between on this roster, because nobody is setting them up.

If you still doubt the impact of the Knicks’ guards, look at the overall offensive results. Heading into last night’s game, the Knicks ranked 21st in the league in Offensive Efficiency, my measure of a team’s points per 100 possessions. On some teams that’s fine, because they’re built for defense — New Jersey would be one example (they’re no. 22, right behind the ‘Bockers).

But the Knicks aren’t a defensive team, as I think even Isiah Thomas would admit. This club was built to win by outscoring teams; if you need any confirmation of this just watch Eddy Curry try to stop Yao Ming. The Knicks came into this season hoping to win games 115–110 by using their high-scoring guards, along with healthy doses of Curry, to outrun and outscore opponents.

That’s where we get into the other part of the problem — the Knicks can’t even play they style they were hoping to because of how the guards play. Isiah Thomas was hoping to play a Phoenixstyle offense that would run like crazy and get lots of transition baskets. But playing this way requires guards who are constantly looking to advance the ball and push it ahead (it also requires a center who can run 94 feet without needing an oxygen mask, but let’s not nit-pick), which is exactly what Isiah’s guards aren’t.

As far as solving this problem, let me go on record saying this isn’t one of those “We need more role players” columns — that always strikes me as tantamount to saying “we need less talent.” The Knicks’ problem, or at least one of them, is reconstructing the talent into a more helpful way.

If they had a deadeye shooter instead of Crawford, it would give Robinson and Marbury more space for their drives. If they had a couple of guys on the wings or the frontcourt who were above-average passers, it might facilitate some easy baskets amid all the difficult one-on-one attempts. And if they had a backup point guard who looked to push the pace and advance the ball, it might be easier to play their running style.

But the Knicks don’t have any of those things. They have four guards who look to score by dominating the ball, and only one of them can have the ball at any one time. As a result, all four of them are going to end up being much less productive than they would in a different environment.

jhollinger@nysun.com