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Analyzing the Starting Pitcher Trades

HOF4BGO and BigCh13f...thebest modeled the impact of trading for a starter

Detroit Tigers v New York Yankees
The Yankees acquired Sonny Gray at the trade deadline, but how much does he really increase their odds of winning yet another World Series?
Photo by Jim McIsaac/Getty Images

The trade deadline has come and gone, and the Astros did not add a starting pitcher to their rotation. In the last few days, many have expressed their frustrations with the lack of a big move at the trade deadline. So we wanted to examine exactly how much of an impact a TOR starter would have made on the Astros chances of winning the World Series.


I collaborated with BigCh13f…thebest to enhance the model he had built for his fanpost and then use the enhanced model to simulate the impact of adding certain starters. Finally, we looked at how the moves that were made (i.e. Sonny Gray to the Yankees, Yu Darvish to the Dodgers) impacted playoff odds.

So if you want more background on the original model, you can read the fanpost. The main enhancements that were made for this simulation were as follows:

-The model now calculates the playoff odds for every team instead of just the Astros

-The model assumes that each team will use 3 starting pitchers in the Division Series, and 4 starting pitchers in the World Series and League Championship Series

-The model assumes that the winner of the Wild Card game will use their ace in the Wild Card game, and so they will be somewhat handicapped during the Divisional Series (i.e. their #1 starting pitcher will only be available for Game 3 of the Divisional Series, similar to what happened with the Astros and Keuchel in 2015)

-Updated Elo scores for teams and pitchers were pulled on Sunday, July 30th

-While the prior model ran 10,000 iterations, we ran 1,000,000 iterations this time to reduce the noise. Since we are examining the impact of changing variables, we want the random noise to be as little as possible.


We assumed the following teams made it to the divisional round of the playoffs:

American League

-Astros (#1 seed) play the Yankees (Wild Card Game Winner)

-Red Sox (#2 seed) play the Indians (#3 seed)

National League

-Dodgers (#1 seed) play the Diamondbacks (Wild Card Game Winner)

-Nationals (#2 seed) play the Cubs (#3 seed)


Our baseline scenario used the top 4 starting pitchers for each of the 8 teams above as of July 30th (so prior to the Sonny Gray and Yu Darvish trades). This gave the following playoff odds for the Astros:

Top 4 pitchers used in playoffs: Keuchel, McCullers, McHugh, Fiers

Odds of winning ALDS: 64%

Odds of winning ALCS: 39%

Odds of winning World Series: 21%

Los Angeles Dodgers v Atlanta Braves Photo by Kevin C. Cox/Getty Images

Yu Darvish

Darvish is a rental (i.e. he will be a free agent at the end of this season), so the idea of trading for him never really appealed to me all that much. Since the Astros are practically guaranteed to make the playoffs, the only reason to acquire Darvish would have been for his performances in the playoffs. Our model showed that he would have increased the Astros playoff odds, but not by much.

Top 4 pitchers used in playoffs: Keuchel, Darvish, McCullers, McHugh

Odds of winning ALDS: 65%

Odds of winning ALCS: 42%

Odds of winning World Series: 23%

Sonny Gray

Gray has a lower Elo rating than Darvish and is generally viewed as a higher injury concern, though he would still have been a member of the Astros beyond 2017. Acquiring Sonny Gray would have also increased the Astros playoff odds, but the impact is even less than that of acquiring Darvish:

Top 4 pitchers used in playoffs: Keuchel, Gray, McCullers, McHugh

Odds of winning ALDS: 64%

Odds of winning ALCS: 40%

Odds of winning World Series: 22%

Justin Verlander

Verlander didn’t get traded at the deadline, and could possibly be dealt as a waiver trade in August though it seems unlikely. His Elo score is between that of Darvish and Gray, and he would be around for one more year although at a pretty hefty price tag. So as you probably guessed, his impact on the Astros playoff odds is similar to that of Gray and Darvish (playoff odds increased, but not by much):

Top 4 pitchers used in playoffs: Keuchel, Verlander, McCullers, McHugh

Odds of winning ALDS: 65%

Odds of winning ALCS: 41%

Odds of winning World Series: 23%

New York Mets v San Diego Padres Photo by Denis Poroy/Getty Images

Jacob DeGrom

This one is just for fun (mostly) and to see how much of an impact a much better pitcher can have. There were rumors at one point that the Astros were talking to the Mets about Jacob DeGrom, but obviously nothing materialized. DeGrom has an Elo Rating of 40, which is considerably higher than the Elo Ratings of the other 3 pitchers we examined (Darvish had the highest of those 3 with a score of 27). In fact, DeGrom would even surpass Keuchel and be the Astros #1 starter in the playoffs:

Top 4 pitchers used in playoffs: DeGrom, Keuchel, McCullers, McHugh

Odds of winning ALDS: 67%

Odds of winning ALCS: 43%

Odds of winning World Series: 25%

So acquiring a dominant ace like DeGrom would have increased the Astros odds of winning the 2017 World Series from 21% to 25%. That’s definitely a measurable impact, but how much are you willing to give up for a four percentage point increase?

Impact of the Trades that Happened

The Yankees acquired Sonny Gray and the Dodgers got Yu Darvish. So what impact did those trades have on the team’s playoff odds, and did they decrease the Astros playoff odds by virtue of those teams getting better?

Yankees odds pre-Gray/post-Gray

Odds of winning ALDS: 36%/37%

Odds of winning ALCS: 17%/18%

Odds of winning World Series: 7%/7%

Dodgers odds pre-Darvish/post-Darvish

Odds of winning NLDS: 72%/74%

Odds of winning NLCS: 47%/50%

Odds of winning World Series: 30%/33%

These are both pretty similar to the impact those pitchers would have had if they had joined the Astros, so no real surprises there. And now for the impact these trades had on the Astros, who didn’t acquire a starter:

Astros odds pre-Trades /post-Trades

Odds of winning NLDS: 64%/63%

Odds of winning NLCS: 39%/39%

Odds of winning World Series: 21%/20%

The results make sense. Our model assumes the Astros will play the Yankees in the ALDS. So since the acquisition of Sonny Gray increased the Yankees odds of winning the ALDS from 36% to 37%, it decreased the Astros odds of winning the ALDS from 64% to 63%. The Astros odds of winning the World Series also took a slight hit due to the fact that they might face the Dodgers in the World Series, and the Dodgers got better with the addition of Darvish.


This simulation only focused on the impact of adding a starting pitcher- specifically, the impact that such an addition would have on playoff odds. Obviously, teams weigh much more than that when making trade decisions. Some of the starters that were traded (Quintana, Gray) will be able to help their new teams in 2018 and beyond so their performance in future years are obviously a big part of the decision to trade for them.

This simulation also didn’t examine the impact of acquiring relievers. That would certainly be interesting to look at since the Astros were rumored to be working on acquiring a reliever, but that’s a much more complicated analysis to perform and we don’t have 40 hours/week to play around with baseball statistics/scenarios unfortunately.

Finally, this modeling made an assumption about which teams would make the Divisional Round of the playoffs, and even which team would enter as the disadvantaged Wild Card team. It’s possible that the Yankees will win the AL East and the Red Sox will be the Wild Card team. It’s also possible that the Mariners win the Wild Card Game and advance to the Divisional Round.


I suppose at this point I could use the results to say either:

1) See! Trading for a starting pitcher would have increased their playoff odds! Instead, the Astros sat idly by and watched their playoffs odds drop while other teams increased theirs!


2) This shows that trading for a starting pitcher would have had a very insignificant impact on the Astros playoff odds, and likely wasn’t worth the prospects that it would have taken to pull off such a deal.

Instead, I’m not going to make either claim. I just want to provide some perspective on the impact that starting pitching trades have on a team’s playoff odds. Is it more or less than you thought? After seeing these results, do you feel like the Astros really lost out on starting pitchers at the trade deadline? DISCUSS!!