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Effects of Intentional Walks on Non-Intentional Walks

Intentional walks (IBB) are usually given to good and/or unprotected players in a lineup. Pitchers would rather face the next, weaker hitting batter. The IBBs lead to an inflated walk rate (BB%) for hitters. By removing IBB from a player’s BB%, a true walk rate emerges. A problem I noticed was that when a player’s IBB% increases so does their non-intentional walk rate (NIBB%). Here is an attempt at putting some numbers behind the assumption.

I have seen the phenomenon of the dual increase a number of times while looking at data. Here are three examples:

Adrian Gonzalez PA IBB NIBB IBB% NIBB
2010 591 35 58 5.9% 9.8%
2011 715 20 54 2.8% 7.6%
2009 674 2 28 0.3% 4.2%
2010 696 14 43 2.0% 6.2%
Paul Goldschmidt PA IBB NIBB IBB% NIBB
2010 (A+) 599 0 57 0.0% 9.5%
2011 (AA) 457 12 70 2.6% 15.3%

Robinson Cano matured into a good hitter in 2010. Pitchers would rather not face him and just walk him. Adrian Gonzalez on the other hand moved from San Diego, where he had no protection in the lineup, to Boston where he had plenty of protection. Both his IBB and NIBB dropped. Like Cano, Paul Goldschmidt became a more feared hitter as his IBB went from 0 to 12. Goldschmidt’s BB% historically should have gotten worse as he went from the High- to Double-A instead of improving. In each of these cases, the NIBB% moved in the same direction as the IBB%.

The two values moving hand in hand logically makes sense. If a batter is feared, pitchers will not throw anything near the zone at times and hope the hitter chases a ball out of the zone. Personally, I have seen way too many non-intentional walks where the pitcher wanted nothing to do with the hitter. While the concept makes sense, there has been no value to show how much of a change should be expected. I tried several methods to determine the amount changed, but found that most players generally don’t have a bunch of IBB. There just seemed a be a bunch of noise when looking at the data. I needed to look at only hitters who actually a decent number of IBBs and a fairly long career.

I looked at established hitters (> 9 MLB seasons) since 1980 who had the highest % of their walks being intentional. I ended up looking at 20 players (Vladimir Guerrero, Barry Bonds, Albert Pujols, George Brett, Miguel Cabrera, Mo Vaughn, Ken Griffey Jr., Eddie Murray, Sammy Sosa, Carlos Delgado, Darryl Strawberry, Will Clark, Dale Murphy, Chili Davis, Bobby Bonilla, Manny Ramirez, Todd Helton, Lance Berkman, Wally Joyner, Albert Belle). For each of the players, I ranked their seasons by IBB% and then split their careers in half by PA and breaks in the IBB rate. Finally I compared the IBB% and NIBB% of the two sets of years and determined how much NIBB% moves in tandem with the IBB%.

Of the 20 players, 14 players saw their NIBB% increase when their IBB% increased. The values ranges from 1.95% increase in NIBB% points for every 1% point increase, to a -1.41% point decrease for every 1% point decrease. The average % point increase works out to +0.50% with a median value of +0.64%. For the sake of ease — and also because there is total lack of acronyms in sabermetrics — I will call the amount of increase in NIBB from IBB “IBBump.”

There are some points to be cautious about when using this data. First, it is just a small sample of data (20 players). Few data points will always be an issue when looking at this data because not that many players have a large IBB%. Generally, only a few hitters are given free passes. The second issue is that I only looked at good hitters. Hitters in the the 8th spot in the NL get quite a few IBB in order for the pitcher to face the other team’s weak hitting pitcher. Those hitters may have a different IBBump value. I wasn’t looking to find all the in and outs of IBBump, I was mainly looking to see if there was any data that backed up my hunch. I see plenty of more work that needs to be done of the subject in the future.

Here is a example of how the use IBBump. In 2010, there was a bit of discussion on how Robinson Cano doubled his walk rate (4.2% BB% from 2005-09, 8.2% in 2010). The first key is to remove the IBB. From 2005 to ’09, he had 14 IBB in just over 3000 PAs. In 2010, he had 14 in almost 700 PAs. By removing the IBB, his NIBB rates drop to 3.8% (for 2005-09) and 6.2% (for 2010). By assuming a IBBump of 0.5 and using his IBB rates (0.5% and 2.0%), the NIBB would drop by 0.2% points for 2005-09 and 1.0% for 2010. The final values work out to be true walk rate of 3.6% for 2005-09 and 5.2% for 2010. These valuse are much closer and show that, in 2010, Cano did not really have that much improvement in plate discipline. In 2011, the lack of discipline showed when his “IBBump adjusted NIBB” dropped to 3.2%

When a hitter has a huge bump in his walk rate, a person needs to look to see if the batter’s IBB went up. Besides just removing the IBB from the data, it seems like even more of an adjustment needs to be made to get a true understanding of player’s plate discipline. More studies should be done on this subject in the future, but initially it looks like a hitter will see bump in their NIBB rate due to IBB increases.