SAN ANTONIO -- Dirk Nowitzki couldn't have looked much more relaxed. He leaned back in his folding chair, propped his right arm on an adjacent seat and even tapped the microphone between questions after taking it out of its stand.

He certainly didn't look like a guy whose 55-win team had just been shoved to the brink of first-round elimination.

Yet that was merely what those watching the postgame press conference on NBA TV saw. By the time he made it to the podium, wearily plopping down in front of a media crowd late Sunday night to dissect the Dallas Mavericks' third successive defeat to San Antonio, Nowitzki had already spent nearly a half-hour sitting and seething in solitude on a training table, unable to put down the stat sheet in his hands.

Nowitzki's relaxed honesty in the interview room was preceded by some blunt regret at his locker once he finally got up off that table. Responding to San Antonio's 92-89 victory and the 3-1 deficit his Mavericks now face, Nowitzki muttered: "If Duncan goes 1-for-9 and Ginobili goes 4-for-16, you've got to win that game."

Got to.

But Dallas couldn't, and didn't. The Mavericks might never again get this kind of welcome in the Alamo City -- where Tim Duncan managed only four points on his 34th birthday and combined with Manu Ginobili and Tony Parker for a mere 31 points as a trio -- and it still wasn't enough. Not even with an 11-point lead at the half to build on.

The Mavs instead submitted another regrettable entry for their playoff meltdown collection, invoking memories of the 2006 NBA Finals and a 2007 first-round flameout against Golden State by giving in to the Spurs' third-quarter physicality. With the Spurs swarming and banging on Nowitzki as much as they were allowed to and a team-wide loss of composure when things got frantic, Dallas mustered just 11 points against a rally inspired by this surprise quartet from the home team: Richard Jefferson, Antonio McDyess, DeJuan Blair and Game 4's hero, George Hill.

Game 5 is thus a win-or-go-home game for the West's No. 2 seeds, after they surrendered home-court advantage in Game 2 to the peaking Spurs and then dropped back-to-back games in San Antonio by a combined seven points.

If you expected more from a group that had the league's best road record (27-14) during the regular season and likewise posted the NBA's gaudiest record in close games -- 18-7 in games decided by five points or less and 35-12 over the past two seasons -- you're not alone.

"It's tough," said Nowitzki said, limited to 17 points and 11 rebounds by McDyess and his help defenders, after scoring 35 points in Game 3. "I'm not going to sit here and lie."

The blow is only slightly softened by the growing realization that the Spurs won't exactly be confused with Golden State in '07. These guys aren't anti-establishment wild cards like those Warriors were. The Spurs have their core of three proven champions and an early candidate for breakout star of the playoffs in Hill, who has shaken the ankle injury that made him a nonfactor in Game 1 to trouble Mavs catalyst Jason Kidd at both ends and step up with a flurry of corner 3s and a clutch 29 points Sunday to bail out the birthday boy.

Exactly a year ago, when Duncan turned 33, Dallas inflicted a Game 4 defeat on the Spurs that gave the Mavericks a 3-1 series lead, ushering Duncan to the brink of the only first-round loss he's ever been a part of. Yet with Hill quickly blossoming, Parker willingly accepting his new sixth-man role and Ginobili on the floor this year -- having taped up his nose, broken in Game 3, and surviving Game 4 without a mask despite Eduardo Najera's around-the-neck takedown in the fourth quarter -- Duncan is suddenly swimming in help.

"[Hill] won the game for them," Mavericks swingman Shawn Marion said.

Added Nowitzki: "They made stuff happen with their defense, and we didn't respond the right way. … They've gotten healthy at the right moment. They're probably one of the best seventh seeds you can run into."

The Mavs, though, never imagined they'd have this much trouble scoring against the intrastate rivals they know so well. They came into this series figuring that the Spurs' razor-sharp team D and noisy fans, however daunting, were nothing they hadn't conquered before. Especially after a midseason trade that seemed to significantly upgrade Nowitzki's supporting cast.

Nor was Dallas expecting to see the Los Angeles Lakers look so vulnerable this early, which significantly raises the stakes of this first-round showdown, because the winner has growing hope of making it all the way to the NBA Finals.

But now, without a dramatic turnaround starting Tuesday night, Dallas will be confronting difficult questions about its future far earlier than anyone connected with the team imagined.

Midseason arrivals Caron Butler and free agent-to-be Brendan Haywood just haven't clicked, which will soon force Mavs management to weigh whether that would change if they're given more time or if the fits just aren't right, no matter how promising they seemed during a 13-game winning streak that is an increasingly distant memory.

One source with knowledge of the Mavericks' thinking conceded that an early exit, furthermore, would only increase the likelihood that they will pursue another roster shakeup this summer, through sign-and-trade bids for marquee free agents.

There is also the small matter of Nowitzki's own future to clarify, as he is eligible for an extension through the end of June and can still opt out of his contract to become a free agent July 1, even though Nowitzki has consistently said he hopes to retire as a Mav. Increasing heat on coach Rick Carlisle is another potential issue, with Carlisle possibly facing more win-now pressure than any playoff coach aside from Cleveland's Mike Brown or Atlanta's Mike Woodson.

One source insisted over the weekend that a first-round exit would not threaten Carlisle's job, just two years into a four-year deal that pays more than $4 million annually and with one year still remaining on Avery Johnson's contract. Yet no one is quite sure how much Mavs owner Mark Cuban will be looking to change if his team can't at least rise out of a 3-1 deficit to drag this to seven games like the Spurs did in similar circumstances in 2006.

"Not pretty," Nowitzki conceded when asked about the Mavs' mindset, not quite believing that he was fielding these sorts of questions already, and too relaxed (or tired) to stop himself from admitting that Dallas' hole is a big one.

"We thought we could get one down here."

Marc Stein is the senior NBA writer for ESPN.com. To e-mail him, click here.

Dimes past: April 4 | 6 | 7 | 8 | 9-10 | 11 | 12 | 13 | 14 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24