In general, strict quant investors will own fewer of the largest, most expensive stocks that dominate the big indexes and gravitate toward under-owned names; will frequently rebalance their holdings to keep their factor exposures consistent; and will cut losses ruthlessly through strict risk-management rules.
Baseball's quants are following along a similar path. Each player's statistical output is compressed into "wins above replacement" – a calculation of how many wins he accounted for, above a hypothetical marginal Major League prospect. Machado is near the top of FanGraphs' projection for 2019 in WAR at between five and six wins. That's a fabulous total, but also a target for a front office to try to approximate with other "portfolio components."
Being able to identify the opportunity cost of not having Machado enables baseball quants to try to gather up pieces of that forgone five or six wins through younger, cheaper relief pitchers with a high swing-and-miss rate, say, or a couple of hard-contact, high-on-base-percentage hitters about to enter their prime and not yet eligible for free agent riches.
In other words, when the performance factors are quantified and treated as fungible, players can be mixed and matched in a cost-effective way to maximize win probabilities.
Not exactly the romantic approach that prevailed when most old baseball fans fell in love with the game – and it's no guarantee of on-field success. But perhaps an inevitable result when big data and big money collide in the big leagues.
Of course, investing and baseball are different in one crucial way. In markets, return on the money invested is literally the entire game. In baseball the point is to win the most games, not get the most wins for payroll dollar. Perhaps that point is being lost by some value-obsessed teams.