PER Diem: Feb. 25, 2009

Tony Parker 66, Dallas 54.

It's amazing but true -- while he was on the floor, one player accounted for more points than the entire opposing team.

Parker did it last night in San Antonio's 93-76 win over Dallas. He had 37 points and 12 assists, plus five of his dimes accounted for 3-pointers -- a total of 66 points. Meanwhile, in the 37 minutes that Parker played, the Mavericks scored only 54 of their 76 total points.

So Parker not only generated more points than the Mavs … he did so by double digits. It was one of the most amazing performances of the season, made even more incredible by the absence of teammates Tim Duncan and Manu Ginobili -- Parker was a one-man band and the Mavs still couldn't stop it. He scored or assisted on all but 13 of San Antonio's points when he was on the court to lead the Spurs to a shockingly easy win.

Of course, every coin has two sides. As incredible as Parker was, his performance was also illustrative of some problems on the other end, and in particular Dallas' struggles in the absence of Jason Terry.

Here's the thing about measuring player performance in basketball: results are always partly dependent on the other players on the floor. This is true for any statistical measure, but it's especially true when we start measuring on-court vs. off-court performance.

Tuesday night's game offered a great example. Dallas's point guard, Jason Kidd, has one of the best on-court vs. off-court plus-minus differentials in the league. (OK, that was a mouthful. What it means is that Dallas scores more points than it surrenders with Kidd on the court than when he's off it.)

However, part of the reason for his unusually strong numbers in this respect is that the Mavs have had other players to cover his weaknesses. In particular, Terry does two things Kidd can't: reliably make open jumpers to keep defenses from cheating on Dirk Nowitzki, and defend opposing point guards who are too quick for Kidd.

Alas, Terry is out with a broken hand. And last night, we saw a good example of what happens with his subtraction. Kidd had the worst plus-minus mark of any Mav, at minus-19, while the absence of Terry allowed the Spurs to suffocate Nowitzki with multiple defenders and permit the likes of James Singleton and Antoine Wright to fire away from distance.

But where Terry's absence was felt most was at the defensive end. Like I said, Kidd struggles against quick point guards -- and Parker is about the quickest point guard in the league.

That continues a trend that's been apparent since Terry went out. Since losing him early in the Chicago game, Dallas has played five games against quick point guards and two games against a team with no point guard (Sacramento); in the two Sacramento games he had the same huge plus-minus he's had all season, but in the others it wasn't pretty: Kidd was a minus-nine in an OT win over Chicago (facing off against Derrick Rose), minus-nine in a home loss to Boston (Rajon Rondo), plus-21 in a 15-point win over New Jersey (Devin Harris), minus-11 in a loss to Houston (Aaron Brooks), and minus-19 against Parker last night. That's minus-27 in five games in which the Mavs as a whole were minus-15.

While this hardly constitutes damning evidence -- game-to-game plus-minus data is extremely variable and thus requires large samples to reach scientifically valid conclusions -- I believe in this case the numbers on Kidd underscore a larger point.

He's been able to register such gaudy plus-minus numbers precisely because the Mavs had the personnel in place to offset his two greatest weaknesses. (This was symbiotic, by the way; Kidd also offsets Terry's greatest weaknesses with his court vision and ability to defend bigger players). Minus his key enabler, however things have quickly gone to pot.

That said, I don't expect opposing point guards to outscore the entire Dallas team on a nightly basis. What Parker did last night was singular and incredible, and worthy of praise regardless of the opponent. But Terry's absence does lay bare a major vulnerability for Dallas, and if he doesn't return soon I suspect it will cost the Mavs a playoff spot.

John Hollinger writes for ESPN Insider. To e-mail him, click here.