Expected Goals (xG) is a Lot Like wOBA
If you understand that not all hits are created equal, you're ready for Expected Goals (xG). In baseball, Weighted On-Base Average (wOBA) assigns a specific run value to a single, a double, or a home run, because a solo shot is obviously more valuable
than a walk. xG does the same for soccer shots. It evaluates every shot based on historical data—considering factors like distance, angle, and defensive pressure—and assigns it a probability of becoming a goal, expressed as a decimal from 0.00 to 1.00. A tap-in from two yards out might be 0.80 xG (an 80% chance of scoring), while a hopeful blast from 35 yards might be 0.02 xG (a 2% chance). Just as wOBA tells you the quality of a player's offensive contributions beyond simple batting average, xG tells you the quality of chances a team is creating and conceding, regardless of the final score. It separates process from luck.
Expected Assists (xA) is All About Creating Value
In sabermetrics, we appreciate the players who set the table. Expected Assists (xA) is the soccer equivalent of valuing the players who create high-value opportunities. An assist in soccer, like an RBI in baseball, can be misleading. A player could make a simple five-yard pass before a teammate unleashes a miracle shot, earning a cheap assist. Conversely, a player could deliver a perfect, defense-splitting pass that a teammate botches. xA measures the quality of the chance created by a pass. It's the xG value of the shot that directly follows a player's pass. So, if a midfielder plays a perfect through-ball that leads to a shot with a 0.60 xG, that midfielder is credited with 0.60 xA, even if the striker misses. It identifies the truly elite playmakers, separating them from those who are just lucky to have clinical finishers on their team.
Progressive Passes and Carries Move Runners Over
How does a team advance the ball into scoring position? In baseball, it's about getting on base and moving runners over. In soccer, the analogous actions are measured by Progressive Passes and Progressive Carries. These stats identify players who effectively move the ball toward the opponent's goal. A progressive pass is generally defined as a completed pass that moves the ball at least 10 yards closer to the goal. A progressive carry is similar, tracking players who run with the ball to advance it a significant distance. These metrics help identify players—often midfielders or even adventurous defenders—who are responsible for breaking down the opposition's defensive structure and starting attacks. They aren't just passing sideways; they are making things happen, much like a hitter who turns a leadoff single into a runner on third with a stolen base and a smart baserunning play.
Pressures and PPDA Measure Defensive Work Rate
For a long time, defensive metrics in soccer were crude—just tackles and interceptions. But like modern baseball fielding stats that go beyond simple errors, soccer analytics now measure defensive intent and effectiveness. "Pressures" is a key stat, counting how many times a player closes down an opponent who is receiving, carrying, or releasing the ball. It measures work rate and a player's role in a team's defensive scheme. Taking it a step further, Passes Per Defensive Action (PPDA) is a team-level stat that shows how aggressively a team presses. It measures how many passes an opponent is allowed to make in their own end before the defensive team attempts to win the ball back. A low PPDA means a team is pressing high and aggressively, like a defense stacking the box in football. A high PPDA indicates a team that sits back and defends deeper. It reveals tactical identity in a clear, quantifiable way.
