Somewhere in a Cubs training room today, Nomar Garciaparra must be wondering, “Was it me?”

Since the moody and finally unhappy shortstop left Boston at the July 31 trade deadline, his former club has been the best in baseball. No one has spent much energy bemoaning Nomar’s absence as the Red Sox have gone 38-16 since August 1, transforming a one-game deficit in the wild card race into a six-game lead and clinching a postseason berth Monday night in St. Petersburg.

To be fair to Garciaparra, the Red Sox’s resurgence was not a simple matter of addition by subtraction – he was having a rough season anyway, bothered by an injured Achilles’ heel and a bruised ego that resulted in large part from the club’s bungled attempt to trade for Alex Rodriguez in the offseason. No, the Red Sox were pouring champagne in the visitors’ clubhouse of the Tropicana Dome largely because of the improvement in the club’s defense that began immediately upon the arrival of Garciaparra’s replacement at shortstop, Orlando Cabrera, new first baseman Doug Mientkiewicz, and utility outfielder Dave Roberts.

Defense is by far the hardest aspect of team play to quantify in meaningful and revealing ways; historically, it has been far down on the list of desired traits in a ballplayer coming to Boston. The 2003 Sox did well enough with the classic all-hit, average-field approach, but this year’s group soon became stuck in a sea of mediocrity after a strong start to the season.

With Garciaparra out of the mix and third baseman Bill Mueller also hurt for a long spell, the Sox infield could be counted upon to muff up a play or two a game. Pokey Reese did a great job of filling in at shortstop, but second baseman Mark Bellhorn’s uninspiring range and mediocre glove- and footwork were exposed daily. First baseman Kevin Millar, meanwhile, displayed the range of a Tonka trunk and struggled to pick up errant throws. The Red Sox allowed a whopping 74 unearned runs through their first 102 games, and their .979 fielding percentage was among the league’s worst.

The Red Sox’s fuel-injected offense could always deliver a whupping on the Blue Jays and Devil Rays, but when it came to close games, the Red Sox defense made far too many costly errors. Then came Cabrera, Mientkiewicz, and Roberts.

One does not have to be from Boston to appreciate the magnitude of this trade. Garciaparra was an icon who, despite his diminished level of play, remained the poster boy of the ball club in the minds of most New Englanders. So when his trade to the Cubs was announced before the middle game of a Red Sox-Twins series in Minneapolis and Mientkiewicz was already filling his new locker before Garciaparra had emptied his, the moment produced more than its share of shock and surrealism.

Contributing to the moment was not just the disparity between Garciaparra’s superstar status and the relative obscurity of his replacements. It was also the spin put on the deal by General Manager Theo Epstein.

“If there was a flaw on the club, it was that the defense on this team was not championship caliber,” Epstein said the day of the trade. “We might have gotten to the postseason but in my mind, we weren’t going to win a World Series with our defense the way it was.”

Huh? Eighty-six years without a championship and all of a sudden the deal-breaker for this team’s chances was better glovework? The reaction to Epstein’s introductory remarks to the post-Garciaparra era was a near-collective snort. In a town that has not seen a Gold Glove season from a player since Tony Pena’s in 1991, the Sox fan base was as ignorant of tight defense as a Kansan is of a knish.

All that has changed. In the 54 games between August 1 and Monday’s playoff clincher, the Red Sox allowed just 17 unearned runs and posted a .984 fielding percentage. Overall, their .981 fielding percentage still places them in the bottom five of the AL but that 54-game rate would place them sixth in the league.

Cabrera, who has missed just two games, does not have the range going to his right of a healthy Garciaparra, but his overall range is better. His range factor – a statistic that adds a player’s putouts and assists per game – since joining the Sox is 4.14, much better than Nomar’s 3.84. While such numbers can be unreliable, Cabrera looks far more comfortable turning a double play and his throws are truer. He is not Garciaparra’s equal with the bat, but the Red Sox did not need Garciaparra to mount one of the most potent attacks in the league.

Mientkiewicz has not been an everyday player, thanks to a season-long slump at the plate and the return of Trot Nixon to right field, where the club would sometimes put Millar when it needed his bat. Depending on the opposing pitcher, Mientkiewicz has been used frequently for Derek Lowe starts, when the ground-ball pitcher needs the best infield he can get. Mientkiewicz has an uncanny knack for making a dazzling stop, whether it is saving an extra-base hit down the first-base line, diving to the second-base hole, or showing an impressive vertical leap to spear a line drive.

Manager Terry Francona has had a difficult time finding ways to start Roberts, but he can play the corner outfield positions and has been making a consistent impact in pinch running situations.

The defensive improvement was encapsulated in a single play on September 23 at Fenway. Orioles shortstop Miguel Tejada hit a sharp ground ball to second baseman Reese’s left. Reese dived to stop it and, from his knees, threw to Cabrera, who was hustling to second base for the force there. A hard, high slide from Melvin Mora forced Cabrera to tap the bag with his foot before leaping high enough to get off a throw to Mientkiewicz, who stretched just far enough to catch the ball before Tejada could reach the bag.

The double play ended the inning, and all three infielders, each with a Gold Glove on his resume, received a standing ovation from the crowd and a conga line of high-fives from teammates heading into the dugout.

Imagine that. The Red Sox can play great defense, and are heading into the postseason with as good a chance as any other team to win the whole thing.

Nomar who?

Mr. Silverman covers the Red Sox for the Boston Herald.