## Monday, October 26, 2009

### Yankees vs. Phillies: Can OPS Tell Us Anything?

The table below shows the team OPS for both the Yankees and Phillies as well as the OPS their pitchers allowed.

So the Yankees have an overall advantage of .081 in OPS. I once found that winning pct = 1.26*OPSDIFF + .5. A team with that big of an OPS differential wins about 60% of their games. So that might be the Yankees probability of winning (although it may not be that simple-I actually came up with about a 72% chance for them to win if they have a 60% of winning each game). Of course, the Phillies did not have Lee or Martinez in their rotation all year. So the differences may not be thaat great in the series and we need to take that into account.

The next table shows the OPS of each pitcher in the rotation for the two teams, in what looks like will be the order for the series. Each pitcher's OPS is compared to the league average.

The next table shows which pitcher has the advantage in each matchup.

The Yankees have a big advantage in each of the first three games. My guess is that it will only be in game 4 that the Phillies have the advantage. Then the rotation starts up again. The Yankee hitters also had an OPS that was .076 better than the league average while the Phillies were only .042 better.

The next table shows some other breakdowns. It shows both hitting and pitching OPS for both teams, home and road and also the league averages for those respective stats.

The Yankees outhit their opponents at home by .129 in OPS. For the Phillies, it is only .037. On the road, these two stats are .082 and .012. So when in Yankee Stadium, the Yankees have an advantage of .117 (.129 - .012). Even in Philadelphia, the Yankees advantage is .045 (.082 - .037).

My guess is that park effects are not a big deal here. The simple average of the OPS in Yankee stadium was about 1.6% higher than in Yankee road games (I simply added what the Yankees hit and allowed at home and divided by 2, then did the same for road games and then the home number was divided by the road number-that is all probably not quite right since Yankee pitchers have more innings at home than Yankee hitters since they don't bat alot of the time at home in the bottom of the 9th). For the Phillies, this was 2.2% higher in home games. So, overall, not much going on with park effects.

Also notice that the Yankees hit .081 better than the league against lefties this year and they get to face 3 lefty starters.

The next table shows how the two bullpens faired compared to the league average bullpens.

So even here, the Yankees have an advantage.

Also, I once calculated that the team with home field advantage wins 51.52% of the time, if the two teams are of equal strength. The Yankees played in the tougher league (the AL has been winning most of the interleague games the past few years). And the other 4 teams in the AL East combined to finish 6 games over .500 outside their division this year. In the NL East, it was 28 games under. So it looks like the Yankees played in a much tougher division, too.