## Rockies Watch

I follow the Colorado Rockies (baseball team), both the games, as a fan, and the stats.

I like the perspective on the game offered by famous expert sabermetrician Bill James' "Pythagorean Relationship". I like it because it uses only two numbers: the team total Runs Scored (RS) and Runs Allowed/Against (RA):

WP = RS2 / ( RS2 + RA2 )

WP is the Winning Percentage. When multiplied by the number of games played it gives the Expected Number of Wins (ENW). Over the course of an entire season this is typically accurate to ±2-3 wins. When the ENW is subtracted from the Actual Number of Wins (ANW) you get the Win Differential (WD):

WD = ANW - ENW

The Rockies ended the season (163 games played) ar at WD = +5¾ .

This was down ~2½ from a season high of 8 1/3 some 22 games earlier, when they were fifteen games over .500 as opposed to nineteen at the end.

A positive WD is usually interpreted as meaning that a team is making the most of its runs scored (over-performing). A team with a WP of .500 and a WD above zero is 2⋅WD wins above .500.

Preferentially winning closer games and losing the lopsided ones is how this is mathematically possible.

The Rockies have had a positive WD all season long.

A closely related number is the Run Differential, RD = RS - RA .

The Rockies have had a negative RD all season until very recently -- like the very last week of the season. It maxed out at -54 seventy-two games in. Despite scoring ¾ run less per game than the other team (54/72=¾ exactly), they were only four games under .500. Then the team went on a remarkable 26 game stretch (centered about on or before the All Star break) where they averaged more than two runs more per game than the opposition. This brought the RD back to zero (+1 actually) -- by this point they were eight games over .500 -- but RD fell back into negative territory after only two days. Twenty-two games later it had dropped back to -24 (after the 1-12 loss in Houston) but they hadn't lost any ground because they were still eight games over .500 . Nine games further along RD was all the way back up to almost break even (-2) and the team was thirteen games over .500 -- before it dropped back to RD = -21 (after the 2nd of two losses in San Diego). Over the subsequent nine games they got RD back up to zero (and went from ten games over .500 to fifteen games over), and for the last dozen or so games RD has been right around zero, ranging from a low of -9 (after getting swept in LA) to a high of +5 -- while they're still fifteen games over .500 . Currently RD = +1.
In the very last week of the season, including a 4-game sweep of the Phillies by a combined 52-10 score. The season then ended, after Game #163 in LA, with RD = +35. It was at a season high of +38 just the day before.

For comparison, the Pirates (78-76) are only two games over .500 with an RD = -9.

The Seattle Mariners (same 85-70 record as us, even down to the Home/Away splits) are even more remarkable than the Rockies with an RD = -35 . They've been even more negative than us in the RD department at least since the All Star break while having a comparable (or slightly better) record much of that time.

With thirty teams, there's almost always one or two teams like this, including those on the other side who are drastically under-performing.

I will try and update this every week or ten days as conditions allow. By this time in the season the numbers usually don't change very much from day to day.

©2018 - Copyright by C.Wetherill: It's okay to reference my work on this page only if you include the address (URL) here so others can see the full page for themselves. I am not in the employ of or otherwise associated with the Colorado Rockies Baseball Team in any way.

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