It wasn't Novak Djokovic's stinging backhand that secured his 3-6, 6-3, 7-6 (3) victory over Tomas Berdych on the first day of Group A play at the ATP World Tour Finals, and it wasn't the Serbian star's slingshot forehand, his ability to transition from defense to offense, or his first serve, second serve, or third serve. It was his aura.

Of course, it didn't hurt that his opponent was a mercurial, world-class head case who can trade shots with anyone but is apt to do his greatest damage when it matters least—as he showed today when, after jumping out to a 4-0 lead and a convincing 6-4 win in the first set, Berdych slowly but inevitably succumbed to a combination of Djokovic's confidence and aura. To his credit, Tennis Channel commentator Jimmy Arias seemed to know what was happening all along, and he forewarned all those trusting souls who interpreted the closeness of the match as a sign that Berdych might actually. . . win.

Fast forward to the third set, and the game after Berdych broke Djokovic for 4-2—as close to a match-deciding break as you could envision. In the very next game, Berdych fell behind, 15-30. He then hit a double fault and followed it up with a whopper of a forehand error to give the break right back. As Arias dryly observed: "This is what happens. . .a win against Novak Djokovic is an event."

It was a pending event that Berdych was not ready to handle, despite the fact that Djokovic presented him with opportunities he denied all his other rivals, including Rafael Nadal and Roger Federer, for first nine months of the year.

Still, as frustrating as it is to watch a two-hour and 40-minute match and end up with a result that seemed almost pre-ordained, you have to give Berdych credit. He was a beast at the baseline. In his first and best set, he served a cringe-worthy 47 percent (actually, one point higher than his overall match stat in that department) yet manged to win 53 percent of second-serve points (contrasted to Djokovic's wobbly 36 percent). He made sure that when Djokovic played defense, it was defensively.

So rewind a bit. Those two early breaks in the first set proved too much for Djokovic to overcome. He started the second set with a statement hold, at love. Berdych got into trouble in the next game, and after four deuces and a break point saved, he capitulated with a forehand error. Djokovic made the early break hold up, although Berdych offered impressive resistance. When each man held with authority in the last two games of the set, it seemed a signal: Game on!

The players held to 3-2, and while the momentum seemed to have shifted to Djokovic by then, Berdych forced him to 30-all in both his service games. If the top seed and world No. 1 was roaring back, it was quietly. As Arias remarked, "We're still waiting for Novak Djokovic to break this thing wide open."

Berdych, meanwhile, was doing something few others were able to pull off this year: He forced Djokovic to play defense in a defensive posture. The feeling here is that it was a combination of Berdych's flat, penetrating shots—and Djokovic's reluctance, or inability, to play with the same zest and aggression that have been hallmarks of his outstanding year.

If the match had a turning point, it was that aforementioned exchange of breaks in the third set, with Berdych unable to secure a 5-2 lead. Although Berdych didn't implode, it was becoming more and more obvious that unless he could step up to seize the match, Djokovic's aura would see him through.

That was never more obvious then when Djokovic faced a match point while trying to send the match into a final tiebreaker. After a spirited, high-quality rally, Berdych was well set up to hit a forehand winner down the line, but he blasted it way wide, prompting Arias to remark: "That was a big miss. He should have made it. It would have been six-feet long even if if it was in (on the sideline)."

That's Berdych: make the impossible shots, miss the ones that are either important or doable (at least against the better players).

Berdych collapsed in the ensuing tiebreaker. He served the first point and lost it with a dispiriting forehand error off the service return. Although he got the mini-break back via Djokovic forehand error, the Serb won the next four points. All tolled, Berdych made three ghastly forehand errors to go down 3-6 in the breaker, and Djokovic closed it out with a service winner.

On the face of it, it seemed a good win for Djokovic. But there are players in this draw less susceptible to aura than Tomas Berdych.

—Pete Bodo