A much-discussed topic within fantasy baseball is the increasing share of wins by relief pitching. In the chart below, you can see relievers won about 100 more games in 2023 than in 2018 (2020 is adjusted to a 162-game season)
The first question is whether the added wins came with more appearances.
Yes, the wins appearance has increased amongst relievers. This makes intuitive sense given fewer and fewer starters reach the required five innings to qualify for a win, meaning a reliever will need to collect the win. Wins per appearance has increased almost 100 basis points from 5.6% in 2018 to 6.5% in 2023.
Knowing where these increased wins emanate can help in fantasy roster construction. Are they from relievers coming into the game early? Or are they courtesy the late-inning group, those also collecting holds and saves, and are generally the higher skilled members of the bullpen?
To study this, Game Leverage (gmLi on Fangraphs) was used to split the reliever population into low, medium and high leverage.
- Low: Below 1.0
- Medium: Between 1.0 and 1.5
- High: Above 1.5.
Which group is responsible for the added wins?
It appears the high-leverage relievers have contributed more to the increase than the other groups. Low and medium-leverage relievers have a flat, to slightly positive uptick across the sample, while high-leverage relievers have seen their winning percentage increase from 6.7% pre-pandemic to 8.1% in the last year three years.
My takeaway is high-leverage relievers may be commensurate to streaming starting pitchers in deep weekly leagues. The percentage of starting pitcher wins declined to 28.8% in 2023. If you were able to roster a high-leverage reliever for three outings in a week (targeting teams with seven-game schedules), they would project for almost the same win contribution as the average starting pitcher: 24.3% vs 28.8%. Considering the reliever would replace your worst starter, the odds are even more in the reliever’s favor. Not to mention, in today’s landscape, the reliever will probably log a save here and there.
