@Philabaseball
Yesterday, I looked at the ZiPS and Bill James projection models and used the two packages to forecast the number of runs the Phillies will score this season.
Here, I'm using the pitching projections from the same two models to estimate the number of runs the Phillies will allow.
For simplicity I looked specifically at ERA and found the averages for the starting rotation and the bullpen. I included 12 pitchers - five starters and seven relievers. The projected ERA's can be seen in the chart to the right. One thing to note, Aumont and De Fratus were not included in the Bill James projection model so I included ERA estimates of 4.00 for each.
Using the Bill James model the starting rotation has an estimated ERA of 3.69 while the relievers sit at 3.40. Using ZiPS the starters have a 3.72 projected ERA while relievers sit at 3.76.
Formula: [SP projected ERA * .66] + [RP projected ERA * 33]
The multipliers are included based on the assumption starters will average six innings per start.
Projected Runs Allowed via ZiPS: [3.72 * .66] + [3.76 * .33] = 3.69
Projected Runs Allowed via Bill James model: [3.69 * .66] + [3.40 * 33] = 3.56
With projected ERA's we can solve to find runs scored by the following: [ERA / 9] * IP]. I estimated 1458 innings pitched by multiplying nine innings by 162 games played. For reference, the Phillies played 1451.3 innings last season.
ZiPS runs allowed projection: 597 | Bill James runs allowed projection: 577.
To compensate for defense I've added 70 runs to the estimated runs allowed total. Last year the defense committed 101 errors and surrendered 62 unearned runs and I believe a slight increase is plausible considering Michael Young's subpar defensive skills at third base.
Including defensive expectations, the ZiPS runs allowed projection is 667 and the Bill James projection is 647.
As I did with the offensive projections and OPS, I'll average the runs allowed projections and settle with 657.
To recap, the models project the Phillies to score 746 runs while surrendering 657 - we can now enter these figures into the Pythagorean Theorem to project the Phillies' winning percentage.
Pyth W%: [(746)^1.81]/[(746)^1.81 + (657)^1.81] = .557
Over a 162 game season a .557 winning percentage works out to a 90-72 record.
How much stock do you put into the ZiPS and Bill James projections?
- Patrick Gordon is the editor of the Philadelphia Baseball Review. Contact him at pgordon@philadelphiabaseballreview.com or @Philabaseball on Twitter.
