What’s wrong with Rory?

Rory McIlroy missed his second cut in a row this week at the Scottish Open. A flurry of news articles and social media posts are likely to follow in the next couple days wondering what’s wrong with Rory. “Where has the lad’s game gone?!” cries a devoted Rory fan — “You can cross him off the list of potential contenders next week.”  tweets a Golf Channel pundit — “It’s simple, really. The deadlifts have finally done him in; this is causing Rory to slump a bit through impact, losing the angle, missing right.” analyzes Brandel.

In my opinion, however, there is nothing wrong with Rory. My argument is simple: golf scores are really random. Below is a density plot of Rory’s scores over the last 2 years.

This is how I like to think of a golfer’s performance; Rory’s score each day (no matter what course he’s on!) is a draw from the above distribution which has mean 2.3, and standard deviation 2.7. Better golfers will have distributions with higher means, and more consistent golfers will have distributions with smaller standard deviations. So, when Rory shoots 2 shots worse than the field, I don’t panic; this isn’t that unlikely (it should happen about 6% of the time).

So, back to Rory’s MC-MC performance over the last 2 weeks. How often should that happen for a player of Rory’s caliber? Well, my sample of data contains the last 2 years, in which Rory played 38 events (I think). I simulate these 38 events 10,000 times (doing exactly what I said above; each round is a draw from the above distribution). I deem Rory to have missed a cut if the sum of his first 2 rounds is less than 0 (so he lost to the field, which should, roughly speaking, result in a missed cut). In 35% of the simulations, Rory had back-to-back MCs at some point in the 38 event sequence.

This is Rory’s first stretch of consecutive missed cuts since May 2015. So, in the 2 year sample I’ve considered, Rory has missed back-to-back cuts on exactly one occasion. This is not unexpected at all, given our simulation exercise above.

Humans love to find patterns in small stretches of data when really there are none. Rory’s poor performance of late is not inconsistent with him still being the same player he’s been for the last few years. That is, he may still be pulling from the same distribution, with mean ~2.3 and sd ~2.7; maybe Rory just had a couple bad draws the last 2 weeks.

Or, maybe he has actually lost it (his putting does look awful). The point is that these last 2 weeks don’t tell us very much about which opinion is the correct one.



3 Replies to “What’s wrong with Rory?”

  1. Completely agree with the Distribution of Scores. Rory will be fine. An intangible variance is that he is still coming off a rib injury. To what extent does it effect him. We do not know.
    Most athletes do not like to divulge too much information regarding their injuries too much. They think it gives competitors a psychological edge.
    “Humans love to find patterns in small stretches of data when really there are none.”
    This is so true and it is still so easy to fall in to that trap. It is simply just another example of Confirmation Bias errors. Yet it is still so frustrating to hear others opinions when they are basing their case on insufficient sample sizes.
    In most discussion it is hard to define what size of sample is large enough to make credible statements.
    In golf it is much harder to trust the size of data that comes only from sources like PGA Tour statistics.
    What may look like a great body of credible statistics, It will still be woefully to small to have any accuracy in forecasting future outcomes.
    That is why I like your Algorithm data so much. 30,000 simulations is much more credible.
    In my opinion you still need to continuously work on controlling confounding variables that can corrupt your data. Then you need to keep adjusting controls to account for tangible and intangible variances.
    No small task when you are trying to encompass a mass of statistics that are derived from only a single sport like Golf.
    Great work you guys.

  2. I’ve always appreciated your work and the way your statistical analysis often adds to my understanding of “whats going on out there”.

    But with all due respect, while I think you mostly reach the correct conclusion on Rory, it’s for the wrong reasons because in Rory’s case you miss the biggest of the big “variable intangibles”… his equipment change. Add that to the other “intangibles”, of his injury and IMO what we have is in effect a “double whammy” on Rory’s career right now.

    It’s been my observations of player results over the years that all players have a level of “streaky” about them. And for the vast majority of players the high quality finishes that result in them either winning prolifically or even keeping their card occur in “bunches”. Rory has been no exception, in fact he might be the poster child for the effect. Go back to his results all the way since 2010 and you see the patterns of him winning in bunches, followed by pauses of everything to good/medium/poor finishes, until he finds another one of those streaks. I believe your analysis is illustrating THAT effect fairly clearly…

    But there are also “intangibles” that cause the “streaking” effect that plugging a players results into a “rote” performance analysis may not account for. Injury, equipment changes, and personal life factors. We rarely know the true “inside” of these players on a personal side and what if anything in their private lives may be affecting their performance, so I won’t even touch those. But the other two are at least “mostly” public so we can inspect those.

    EQUIPMENT – If Rory’s 2013 year is any example, it would appear as though he had an tough time adjusting to his equipment change from Titleist to Nike. That would be no surprise as we’ve seen that pattern by other top tier players who’ve made wholesale equipment changes during their careers. It took a late season win in a fairly “poor field” event in Australia to prevent Rory from having his only “0-fer” season in terms of winning since 2009. This year, with Nike exiting the equipment business, Rory has been forced into another equipment change.

    The reason these equipment changes are such a huge factor is due to how so little of a variance of result as a player gets used to his new equipment can greatly affect their scoring. You may not recognize it so much in their driving, because if a ball is carrying 310 vs 325 into the FW who notices? We probably think all are still great drives. But take even a 5-7 yard variance of distance or L to R dispersion into the approach to the green and you’ve got big, big issues for players of this level.

    Putting is the same issue. If from 15′ a player’s L/R dispersion increases even an inch or two due to lack of experience with a piece of equipment, and/or his speed variation increases by even 5%, a guy can look like he’s gone from a great putter to “not being able to putt his way out of a paper bag”.

    INJURY – Now lets add the back/rib injury into it. Rory claims that it doesn’t affect his swing while playing, but it has greatly affected the amount and way he can practice. He’s not hitting as many balls, plus he’s missed a lot of events. On top of that the MC’s are subtracting competitive rounds. So that’s yet another “change” that Rory has to deal with at the same time. IMO, and if history is any indicator, the equipment change for Rory will work itself out when he gets sufficient practice and plays enough with it, but it takes time. And if history is any indicator, once Rory either heals from or adapts to an injury, he gets back to form pretty quickly. But this time Rory’s got a bigger challenge adjusting to the equipment and getting his “reps” because the injury has prevented him from doing so.

    BOTTOM LINE – When a player of Rory’s caliber says “he’s close”, he’s often derided by those who don’t understand the game at the level “those guys” play it. But most of the time the player is absolutely correct. The difference of result between contending and MC’ing in any given week is a way slimmer margin for a top player than most people realize. One bad drive on just one hole, coupled with one missed approach on another hole, coupled with 2 lipped putts in a round can be the difference in shooting 66 and 73… A couple of 66’s and a guy could be leading… a couple of 73’s and he’s trunk slamming.

  3. “Well I try to make a very complex variablistic game and try to understand it, to understand every single variable in this whole game of golf.”
    Bryson DeChambeau

    That should be the same goal for creating the best Golf algorithm.

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