For most of baseball's history, batting average — hits divided by at-bats — was the dominant measure of offensive performance. The sabermetric revolution of the 1980s–2000s revealed its critical flaw: batting average treats a walk as worth zero, values a single and a home run equally per event, and ignores hit-by-pitches and sacrifice flies. OPS corrects two of these problems simultaneously: OBP captures the ability to reach base (including walks and HBP), and SLG captures power output per at-bat. Their sum provides a single-number offensive rating that, while imperfect, correlates more strongly with run production than batting average.
Why OBP Matters More Than SLG
The two components of OPS are not equally valuable. Research using run expectancy frameworks consistently shows that OBP is worth roughly 1.8× more than SLG in terms of run production. This makes intuitive sense: you cannot score without first reaching base. A player with OBP .400 and SLG .400 (OPS .800) is considerably more valuable than a player with OBP .300 and SLG .500 (OPS .800) despite identical OPS values — the first player reaches base 33% more often. OPS's flaw is treating both components as equally weighted despite their different denominators and run values. wOBA corrects this by using empirically derived run values for each batting event, but OPS remains the more accessible stat because it can be computed mentally from a box score.
wOBA: The More Precise Alternative
Weighted on-base average (wOBA) assigns each plate outcome a linear weight proportional to its actual run value. The 2024 MLB linear weights are: walk = 0.690, HBP = 0.722, single = 0.888, double = 1.271, triple = 1.616, home run = 2.101. These weights are derived from run expectancy matrices — the expected number of runs scored in the remainder of an inning, averaged across all base-out states, using millions of play-by-play records. A home run is worth 2.101 in run value, not 4 (as SLG implies), because not all home runs come with runners on base. Similarly, the difference between a walk (0.690) and a single (0.888) reflects that singles advance existing baserunners while walks do not force the same advancement. wOBA is scaled to match OBP numerically, making it intuitive: .340 is league average; .400 is elite. For cross-era comparisons (e.g., comparing a 1960s hitter to a 2020s hitter), wOBA is more appropriate than OPS because the linear weights can be era-adjusted.
Using OPS for Player Evaluation
OPS is most useful as a quick screening tool and relative comparison stat. The tiering system — Elite (1.000+), Great (.900–1.000), Above Average (.800–.900), Average (.700–.800), Below Average (.600–.700), Poor (<.600) — maps to historical MLB data: approximately 5% of qualified hitters reach 1.000+ OPS in a season; 15% reach .900+; about 50% fall between .700 and .850. When evaluating a player across seasons, watch for OPS components diverging: a hitter whose OBP stays constant while SLG drops likely stopped pulling the ball or lost power; one whose SLG stays constant but OBP drops may be trading patience for aggression. Park-adjusted OPS+ addresses another limitation: a .750 OPS in Coors Field (high altitude, favorable to hitters) is less impressive than .750 OPS in Dodger Stadium. For fantasy baseball purposes, raw OPS is sufficient; for roster construction, pairing OPS with strikeout rate, walk rate, and exit velocity provides a more complete picture.