Winning the offseason — signing the marquee free agent and/or making the headline-grabbing trade — does not correlate strongly with actual winning. The San Diego Padres “won” the 2014-15 offseason by adding Craig Kimbrel, James Shields and a host of other players, then went on to lose 88 games the following season. The previous winter, Seattle shocked the baseball world by outbidding the Yankees for All-Star Robinson Cano, but the Mariners still haven’t made the playoffs since 2001. In December 2011, the Los Angeles Angels signed Albert Pujols to a 10-year, $240 million contract — a contract that quickly became one of the great albatrosses in the sport. The deal has compromised the Angels’ ability to improve their club; Angels star Mike Trout has participated in only three playoff games in his career.

But last winter, something unusual happened: The Milwaukee Brewers won the offseason and went on to win in the actual season. The Brewers, who will begin the National League Championship Series against the Los Angeles Dodgers on Friday, acquired the best player in the trade market last winter in Christian Yelich and the best player in the free-agent market in Lorenzo Cain. They also found an undervalued arm in Jhoulys Chacin.

These big-name acquisitions exceeded expectations. In total, no team had a better year-to-year roster overhaul than the Brewers — and it wasn’t close.

The Brewers added 18.90 wins above replacement from outside their organization in 2018. The next closest teams were the Tampa Bay Rays (11.93 WAR) and Houston Astros (9.05). In terms of net gains and losses from last offseason, the Brewers’ departing players accounted for -0.02 WAR of value in 2018 with their new teams, making their net WAR gain from offseason transactions 18.92. The next closest clubs? The Red Sox (7.78) and Reds (5.43). Yelich (7.61 WAR), Cain (6.30) and Chacin (2.50) accounted for 39.7 percent of Milwaukee’s WAR this season.

The Brewers won the offseason … and the NL Central MLB teams by net wins above replacement (WAR) for the 2018 regular season team Net WAR Milwaukee Brewers +18.92 – Boston Red Sox +7.78 – Cinncinati Reds +5.43 – Cleveland Indians +3.97 – Toronto Blue Jays +3.95 – New York Yankees +3.77 – San Francisco Giants +3.33 – Minnesota Twins +3.26 – Houston Astros +2.73 – Philadelphia Phillies +2.15 – Atlanta Braves +1.94 – Tampa Bay Rays +1.84 – San Diego Padres +1.48 – Los Angeles Dodgers +1.45 – Seattle Mariners +0.73 – Colorado Rockies -0.47 – Oakland Athletics -0.49 – Texas Rangers -1.46 – Washington Nationals -1.53 – New York Mets -1.84 – Baltimore Orioles -2.47 – Pittsburgh Pirates -2.49 – Chicago Cubs -5.55 – Los Angeles Angels -5.81 – Arizona Diamondbacks -5.91 – Chicago White Sox -5.93 – St. Louis Cardinals -13.27 – Miami Marlins -13.59 – Detroit Tigers -15.01 – Kansas City Royals -16.22 – Sources: Fangraphs, Baseball-reference.com

One reason it’s so difficult to translate offseason success to the actual playing field is that predicting player performance is a difficult task in just about every sport — even a sport rich in data like baseball. Injury and misfortune can derail the best of plans.

Another reason is tied to a macro-level trend in baseball: Free agency has been devalued.

Because of both performance and financial motivations, teams are prizing cheaper, younger talent more. The average age of an MLB player in 2004 hit a post-World War II high of 29.2, but that has gradually declined to a 21st-century low of 28.2 years this season. Testing for performance-enhancing drugs, which began in earnest in 2004, has also likely played a role in the disappearance of 30-somethings — ages when players are typically acquired as free agents. Simply put, it’s more difficult to buy a competitive team in baseball, while the Chicago Cubs and Houston Astros have won titles with homegrown efforts and given MLB a blueprint in the past several seasons.

Yet Milwaukee defied the odds and — partially through spending — got itself a contending team. As the industry zigged, the Brewers zagged.

Conventional wisdom has it that small-market baseball teams must be homegrown because there is no financial mechanism like a salary cap to level the playing field, though baseball’s strengthened penalties for exceeding the luxury tax are acting something like a soft cap. But the Brewers, ranking 23rd in opening day payroll, had the second lowest amount of homegrown production this season, according to MLB.com’s Mike Petriello, who found that only the Oakland A’s had a lower share of homegrown WAR than the Brewers’ mark of 17 percent.

The Brewers’ offseason and in-season success is tied to being opportunistic. The team took advantage of a suppressed free-agent market to land Cain, an effort perhaps aided by clubs saving dollars to pursue Bryce Harper and Manny Machado this coming offseason. Star-level free agents often sign before New Year’s Day, but it wasn’t until late January that Cain reached a five-year agreement worth $80 million. While the back end of the deal might not turn out to be favorable for the club, the 32-year-old Cain’s 6.3-win season has already covered much of the expense in terms of performance value. Among 2017-18 free agents, no one was more valuable than Cain this season — even J.D. Martinez, who is guaranteed $30 million more over five years.

While teams have become more leery of free agency, they’ve also become less likely to part with prospect talent. Milwaukee went against the grain here, too, in acquiring Yelich, who may very well be the NL MVP. The Brewers surrendered four prospects — including their top prospect, Lewis Brinson — to acquire Yelich. The 26-year-old is under club control through the 2022 season at $51.3 million.

All clubs are interested in free-agent bargain hunting to fill out their rosters — and the Brewers did well here, too, in signing Chacin to a two-year, $15.5 million deal. Chacin’s 2.50 WAR was third only to Miles Mikolas (4.47 WAR) and Jake Arrieta (2.65 WAR) among free-agent starting pitchers signed over the winter.

With the Brewers, Chacin and Yelich have gotten more out of their abilities. Chacin’s slider usage rate has increased to a career-high 43.9 percent; in run value per 100 pitches, it was the 11th-best slider in baseball. Yelich became more aggressive in swinging in early counts in the second half, and his home run-to-fly ball rate surged to 48.1 percent.

The Brewers were also able to avoid the overpriced relief market, returning Josh Hader and Corey Knebel — their top two relievers from 2017. Their bullpen is the strength of their pitching staff.

Milwaukee invested wisely. The Brewers saw undervalued players and opportunity last winter. Because of that, this high-import, small-budget team is four wins from the World Series.

Neil Paine contributed research.

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