The answer the film supplies is that by employing the analysis of newly recruited assistant general manager Peter Brand (a fictional version of Paul DePodesta, who was an actual assistant to Oakland general manager Beane), the A's were able to break down the contributions of the departed players to their component elements and comb the market for undervalued players who could collectively contribute in similar ways.
It shouldn't be a spoiler to baseball fans that the 2002 A's did indeed return to the postseason by winning 103 games and the AL West title. However, exactly how they did it was quite a bit different than how both the film and the book suggest. In reality, the approach that came to be hailed as Moneyball was just one piece of the puzzle that made Oakland a perennial contender from 2000 to '06, when it averaged 95 wins, captured four AL West crowns and made five playoff appearances.
The Moneyball revolution is born in the film in a scene in which Beane, with Brand in tow, holds a meeting with his scouting staff and informs them that he plans to fill the hole free agency has created in the A's offense with former Red Sox catcher Scott Hatteberg, aging Yankees star David Justice and Giambi's younger brother, Jeremy. Though the meeting is a piece of fiction, the dialogue is drawn directly from a passage in the book in which the 2001 on-base percentages of the elder Giambi (.477), Damon (.324), and designated hitter Olmedo Saenz (.291), who was "headed for the bench," are averaged to produce a .364 OBP that Beane and DePodesta hope the younger Giambi, Justice and Hatteberg (who averaged a .352 OBP in 2001) can replace.
The biggest problem with the idea of those three as this trio of "Moneyball" players who were picked off the scrap heap to help return the A's to glory in 2002 is that Jeremy Giambi played 124 games and made 443 plate appearances for Oakland in 2001. This is completely ignored in the film, which opens with the A's losing the 2001 Division Series to the Yankees but makes no reference to that series' most famous play, when the younger Giambi failed to slide on the famous Derek Jeter flip throw to home plate in Game 3.
Even the book makes only a passing reference to one of those three players being "promoted from within the organization." In fact, Jeremy Giambi actually saw more major league playing time than Saenz in 2001, and as things played out, Giambi and Saenz combined for 784 plate appearances with Oakland in 2001 and just 365 PA with the A's in 2002. So Jeremy Giambi wasn't so much replacing anyone as he was being replaced himself.
Another problem with the way the film portrays the dilemma of replacing the elder Giambi, Damon and Isringhausen is that the latter two were rather easy to replace. Damon had his worst major league season in 2001 and Isringhausen was a closer who threw just 71 1/3 innings that year. The film makes a big show of the player banners hung on the exterior of the Oakland Coliseum, showing ones for Giambi, Damon and Isringhausen resplendent during the 2001 ALDS only to come crashing down—along with Beane's spirits—as all three depart as free agents that winter. The next season, there is just one lone banner—that of the faded star Justice.
However, the three departing players were in no way equals coming out of the 2001 season. As Lewis clearly states in the book, "...the departures of Johnny Damon and Jason Isringhausen, both proven stars, were not great blows to the Oakland A's."
According to Baseball-Reference's Wins Above Replacement (bWAR), Damon, who hit just .256/.324/.363 in 2001, was worth 2.7 wins above replacement that season, making him the A's fifth-most valuable non-pitcher. Isringhausen, who had a fine season as Oakland's closer in '01, was worth 2.2 wins above replacement, making him the team's fifth-most valuable pitcher. Those two thus combined for 4.9 wins above replacement, less than half of the 10.3 wins credited to Giambi.
Though the film doesn't address it, the A's replaced Isringhausen perfectly by flipping minor league third baseman Eric Hinske and minor league righthander Justin Miller to the Blue Jays for their closer, Billy Koch. Hinske won the American League Rookie of the Year award with Toronto in 2002, but saw his value halved in 2003 and hasn't been worth more than a single win above replacement in any season since. Koch, meanwhile, threw 93 2/3 innings for Oakland in 2002, matching Isringhausen's value exactly (2.2 bWAR). At season's end, he was then flipped to the White Sox in a deal that brought in his replacement, Keith Foulke, who was even more valuable in 2003, but left as a free agent himself, joining Damon on the 2004 World Series champion Red Sox.
There's a thread to follow there about the fungiblity of relief pitching, the A's disregard for the so-called "closer mentality" in employing set-up men Arthur Rhodes and Octavio Dotel in the role in 2004 and their success with home-grown closers Huston Street, Brad Ziegler and Andrew Bailey ever since. The film doesn't have time to follow it, though, and doesn't bother to clutter its dialogue with the idea that closers having more perceived value than actual value is another market inefficiency for low-budget teams to exploit.
Getting back to the 2002 A's, the new pieces didn't fit as well in the lineup as the old ones had. In terms of the defensive alignment, Hatteberg did replace Jason Giambi at first base in '02, and by pushing 2001 leftfielder Terrence Long into Damon's vacated spot in center, Justice did replace Damon in the outfield. However, Hatteberg and Justice, despite averaging a .375 on-base percentage, did not fully replace the production of Giambi and Damon, who had combined for 13 wins above replacement in 2001. In fact, they didn't come close, combining for just 4.1 bWAR.
Justice got on base, but his power was gone and he played in just 118 games, losing most of May to injury. As a result, he failed to match even the low standard set by Damon in 2001, batting .266/.376/.410 with 11 home runs.
Hatteberg, who hit .280/.374/.433 with 15 homers, was nearly twice as valuable as Justice, but he was tasked with replacing the irreplaceable, a season in which Giambi followed his AL MVP campaign of 2000 by hitting .342/.477/.660 in '01. Hatteberg managed to fill only a quarter of that hole in terms of wins above replacement.
To make matters worse, Long wasn't up to the challenge of centerfield and collapsed into a replacement level player, costing the team another two wins. (There's a moment in the film when Beane tells his manager, Art Howe, that "fielding doesn't matter," which feels particularly dated given that team defense was the market inefficiency that the Rays exploited to win the AL pennant in 2008).
Per the following table, even after adding Justice and Hatteberg and moving Long, the A's still had a Giambi-sized hole to fill, a larger one in fact, on the order of 11.1 wins above replacement:
So, where did the 2002 A's find those missing 11 wins? The cold hard fact is that it was mostly luck. As portrayed in the film, Beane got fed up with Jeremy Giambi's off-field behavior in late May and, per the book, "in a silent rage, Billy called around the league to see who would take Jeremy off his hands. He didn't care what he got in return. . . . The Phillies offered John Mabry. Billy hardly knew who John Mabry was." Mabry was a 31-year-old journeyman who had hit .271/.324/.397 to that point in his career, but he had a hot four months for the A's and added two wins above replacement to their ledger as a corner outfielder and first-baseman. (Note that, in the film, Beane trades Giambi and rookie first baseman Carlos Peña in a single outburst, needing just two terse calls to the Tigers to unload Peña. In reality, Peña was traded more than a month after Giambi in a three-team, seven-player mega-deal that also involved the Yankees, Tigers ace Jeff Weaver, a young Ted Lilly and Oakland's 2001 first-round draft pick, Jeremy Bonderman, and surely took more than two brief calls to orchestrate.)
That leaves nine wins unaccounted for. According to Pythagorean record, a team's projected record based on the number of runs they scored and allowed, the A's actually were eight wins worse in 2002 than they were in 2001, they just outplayed their own ability by roughly the same amount.
It's not hard to see how luck played a role in Oakland's success in 2002. Just look at its record in one-run games. A team's records in such games usually trends toward .500 because those contests are hardly more effective than coin flips in illustrating which team is actually better. In 2001, for example, the 102-win A's went 21-19 in one-run games, just one game better than .500 in an equal number of games (20-20). In 2002, however, Oakland went 32-14 (.696) in one-run games. In 2003, the club fell back to 25-20 in one-run games and won 96 games overall, exactly the number of wins in its 2002 Pythagorean record.
What is emerging here is the fact that, from 2001 to 2003, the A's, even after losing Jason Giambi, maintained a level of play that put them around 95 wins annually (their 104 Pythagorean wins in 2001 minus Giambi's 10 wins above replacement put them right around that number). Ninety-five wins would have been enough to earn the A's the wild card in 2001 and '02 and the AL West in '03. The extra wins they piled up in 2001 did them no good because the Mariners won 116 games, and winning the division rather than the wild card in '02 did them no good as they were dispatched in the first round of the playoffs by the Twins anyway. The whole issue of replacing Giambi thus becomes moot.
As to what made Oakland so good even without one of the top run producers of the day, here are the five most valuable players on the team's 2002 roster, according to bWAR, along with when and how they entered the organization:
1997, draft (sixth round)
1999, draft (first round)
1993, amateur FA
1998, draft (first round)
1996, draft (first round)
Hudson, Zito (the Cy Young winner that year) and Mulder were a stellar trio of young starting pitchers who were known as the Big Three and anchored one of the best starting quartets in the game's history. Tejada won the AL MVP in '02 after hitting 34 home runs and driving in 131 runs and Chavez was a Gold Glover and Silver Slugger winner that year. None of those players came out of Paul DePodesta's computer. DePodesta had joined the A's in 1999 (not following the 2001 season, as is the case with the film's fictional Peter Brand) and, according to the book, didn't participate in the draft until 2002.
However, that isn't a reason to dismiss the importance of DePodesta and statistical analysis in Oakland's success. A replacement level team would win roughly 50 games. The players above were worth 26.2 wins in 2002. Upgrading a replacement level team with those five players alone wouldn't even result in a winning record. To turn that core into a perennial contender, Beane and DePodesta had to tease another 20 wins above replacement out of one of the smallest budgets in the game.
That is where the term "Moneyball' comes from. It isn't about trying to turn water into wine by pretending Scott Hatteberg can replace Jason Giambi. It is about wringing the maximum number of wins out of each additional dollar by identifying value where other teams have yet to detect it. It's about marginal wins, the ones that separate a playoff team from a runner up. It's about getting over the hump.
Scott Hatteberg was the third most productive non-pitcher on the 2002 A's. He cost $900,000 because no other team recognized his value as an on-base threat or his potential to move to first base after elbow problems put his career as a catcher in jeopardy. He cost the A's $333,333 per win above replacement in 2002. Jason Giambi was nearly three times as productive as Hatteberg in 2002, but he cost the Yankees more than four times as much per win, making Hatteberg far more valuable on a dollar-for-dollar basis.
Hatteberg was the 2002 A's greatest success story, but Beane and DePodesta deserve credit for far more. The three-team trade that brought Damon to Oakland prior to the 2001 season and rid the A's of Ben Grieve and Angel Berroa—two other players who, like Hinske, fell off steeply after winning the AL Rookie of the Year—also brought second baseman Mark Ellis and righty Cory Lidle to Oakland. Lidle became the fourth starter and combined with Ellis for 5.7 wins above replacement in 2002.
Meanwhile, Damon's departure as a free agent netted Oakland the compensation draft pick with which it claimed Nick Swisher in June of '02. A deadline deal one month later for pending White Sox free agent second baseman Ray Durham added another win and two more draft picks.
Add up Durham, Ellis, Hatteberg, Justice, Koch, Lidle and submarining righty reliever Chad Bradford, and that's 14.5 of those 20 marginal wins right there. Of those seven players, only Justice and Lidle were paid seven figures by the A's in 2002. Only Justice, who was having more than half of his salary paid by the Yankees, cost Oakland more than a million dollars per win. The A's didn't pay Durham a dime, as the White Sox covered his entire salary in exchange for minor league righty Jon Adkins.
That last is a credit to Beane's savvy on the trading block, which is illustrated in the film in a scene taken directly from the book in which he plays three teams off each other in order to acquire lefty reliever Ricardo Rincon, and is further evidence that success has many fathers.
So did the A's win because of Moneyball? Well, sort of. They won because they had a core of high-ceiling talent identified by their scouts, because they were able to supplement that core with cost-effective role players identified by DePodesta's analysis and because Beane made a number of savvy trades that resulted in both player upgrades and salary relief. Take away any one of those elements, and we're no longer talking about a playoff team, and we're almost certainly not going to be watching a movie about them.