Team Strength Rating (TSR)

The Team Strength Rating answers one question: if two teams played on a neutral field tomorrow, who would win, and by how much? It is measured in runs. The average team in a division is 0 every season, so a team at +5 is five runs better than that season's average team.

D1 baseball has three parts:

• Adjusted offense (AdjO) and adjusted defense (AdjD): the runs per nine innings a team's offense scores, and its pitching and defense allow, against an average D1 team at a neutral park. Both are adjusted for the opponents faced and are measured with expected runs, so they credit the quality of the at-bats, not the luck of when the hits came.
• Wins and losses, adjusted for the strength of the schedule.

Early in a season, a team's offense and defense are pulled toward its preseason projection. The pull shrinks as games are played.

D2, D3 and NAIA baseball, and softball use a rating built mainly from a team's underlying statistics, with a smaller share from its schedule and results.

Subtract one rating from the other to get the expected margin on a neutral field. If one team is +5 and the other is +2, the first is expected to win by about 3 runs. Home field adds about 0.8 runs for the home team.

For AdjO, higher is better. For AdjD, lower is better: it is runs allowed.

• ratings: power_rating for every team, current.
• ratings/{date}: the ratings as they stood on any day of the current season.
• stats: Rating, AdjO, AdjD and their ranks, for any season.
• baseball/d1/daily-ratings/{date}: D1 baseball, day by day, for finished seasons.
• baseball/combined-ratings: all four baseball divisions on one scale.

• Early in a season the rating leans on the preseason projection, so it moves slowly at first.
• A rating is relative to its own division. Use the combined ratings to compare baseball divisions.
• Seasons from before play-by-play was available use actual runs in place of expected runs.
• It describes how strong a team is, not what it has earned. For that, use PCR.