If you spend any time reading RotoViz, eventually you’ll hear us talking about expected points. Expected points (EP) are the number of fantasy points that a target or carry should score based on game situation — down, distance, and field position. In other words, expected points allow us to transform raw opportunity, such as carries and targets, directly into fantasy points. From there we can look out how players actually perform with their opportunity — how many points they actually score — and arrive at a player’s fantasy points over expectation (FPOE). FPOE turns out to be a catch-all efficiency metric that accounts for both yards and touchdowns in a single number. Add EP (opportunity) and FPOE (efficiency) together, and you get a player’s actual fantasy output.
But you might also wonder why we care so much about expected points? What do EP and FPOE tell us that simple PPR points do not? And how should we be using EP and FPOE data to inform our fantasy decisions?
To answer these questions, I dropped all the 2019 numbers we’ve been tracking in this column into a series of correlation matrices — one for each position. The vertical axis lists Week N metrics, while the horizontal axis lists Week N+1 metrics, so you can read down the list and scan across the matrix to find out how predictive your favorite metrics are from one week to the next. Things should become clear as we go through each matrix.
The way to read the matrix above (and all those below) is to find a metric on the vertical axis and then scan across to see how well it correlates with some other metric in the following week. So, starting at the top, we find total EP. If we look across the top row to the very end, we find that EP has a 0.235 correlation with PPR points in the following week. If we then scan down to the bottom right corner, we also find that this is slightly higher than the 0.23 correlation PPR scoring has with itself in the following week. So expected points predict future PPR points better than PPR points do.
By far the most stable — and most predictive — quarterback metric is market share of total EP. A quarterback’s share of his team’s total EP in one week is the only metric that has at least a 0.3 correlation with fantasy scoring in the following week. And because nearly every QB accounts for 100% of his team’s passing EP, this tells us something important about the QBs that score well in a given week. The two ways a QB could excel at msEP are by accounting for a large portion of his team’s rushing EP, or by his team having a large portion of their overall EP come from the passing game. For fantasy purposes, we generally only want to chase the former (with a few exceptions).
We have two great examples this season. Lamar Jackson leads all QBs in msEP — in fact the only player accounting for a higher percentage of his team’s total EP is Christian McCaffrey. After Week 15, Jackson leads all players in PPR points, edging McCaffrey by just 1.6 points.