xG measures the quality of a chance. A penalty = 0.76 xG. A header from 15 yards = 0.07 xG. If a team has 2.5 xG and scored 1 goal, they were unlucky. If they had 0.5 xG and scored 3, they were clinical. Over a season, xG is the most reliable predictor of actual ability. Teams that consistently outperform their xG regress. Teams that underperform their xG improve.
PPDA measures pressing intensity. Lower = more aggressive pressing. Liverpool under Klopp had a PPDA of 7-8 (extremely high press). A team with PPDA of 15+ is sitting deep and letting opponents pass freely. If you want to know who presses hardest in Europe, sort by PPDA.
A pass that moves the ball at least 10 yards toward the opponent's goal. Measures who actually moves the ball forward vs. who passes sideways. Toni Kroos led Europe in progressive passes for 5 consecutive years. It's the stat that separates creators from passengers.