Editor’s Note: This is an excerpt from Rich Hunt’s 2017 Pro Golf Synopsis, which can be purchased here for $10. Stylistic changes were made to the story for online publication.

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At the start of the 2015-2016 season, PGATour.com introduced the Strackaline app to ShotTracker. The app provides 3D topographical scans of each green on the PGA Tour, but its presence with the Tour was short-lived. By early 2016, the Tour stopped using the app in conjunction with ShotTracker. I found the Strackaline app to be helpful in exploring something we have long wondered about; how well Tour players putt on different types of breaking putts.

I was excited to use this app for my own Tour clients to help them with their putting, and I started to notice some interesting trends. Poor putters putted differently from average putters, and average putters putted differently from great putters. Some characteristics started to emerge when players putted significantly better than normal, as well as when they putted significantly worse than normal.

I then used that data and explore other random players: great putters, better-than-average putters, average putters, worse-than-average putters, and the worst putters on Tour. I was interested in seeing how different golfers putted from certain locations on the Fall Line Clock to see if there were any similar characteristics or trends with their putting.

Methodology

The Tour’s decision to stop using the Strackaline app made my research more difficult. The good news is that the Strackaline app has a function that allows you to place the pin in the position where you think it is located on the green. Then you can place a golf ball on a spot on the green and Strackaline will give the distance to the hole, as well as the contours of the particular putt and where exactly golfers should aim.

Granted, I cannot say that I was 100 percent accurate on my estimations of flag and putt location, but I did examine the following putts:

1. Putts that were on a very planar slope.

These are putts that have one break to them and are not double breakers. They don’t sit on a crown or in a “saddle.” I tried to get putts that were essentially right on one particular position on the Fall Line clock. Any putt that was too difficult to tell, I did not record the data.

2. Putts from 4-20 feet.

These are makeable putts that require more precise green reading, aim, touch/speed and stroke mechanics. I examined 38 right-handed-putting Tour players ranging from excellent putters like Luke Donald and Mackenzie Hughes to the worst putters on Tour like Boo Weekley and Robert Garrigus. In particular, I sighted events where the player was either greater than 1 standard deviation in Putts Gained for the entire event or worse than 1 standard deviation in Putts Gained for the entire event.

Matt Jones was a player I examined. For the 2016-2017 season, his Putts Gained was +0.170 per round. His standard deviation for the year was 0.7092. So I researched two events that he was greater than +0.8792 strokes per round (the AT&T Pebble Beach Pro-Am and The Greenbrier Classic) along with the two events where he putted worse than -0.5392 strokes per round (the AT&T Byron Nelson and the Shell Houston Open). I also examined four more events for Jones that were right around his average for the season.

Here’s a representation of the Fall Line Clock from golf instructor John Dunigan.

Twelve and 6 o’clock represent straight putts (12 o’clock is a straight downhill putt and 6 o’clock is a straight uphill putt). Putts from 4 to 8 o’clock are on an uphill gradient, and putts from 10 to 2 o’clock are on a downhill gradient. Putts from 1 to 5 o’clock break to the left, and putts from 7 to 11 o’clock break to the right.

Lastly, I normalized the data so the putting performance from each position on the Fall Line Clock would represent a probable make percentage from 10 feet. On average, 10-foot putts have a 38 percent make percentage on Tour.

Make Percentages from Different Locations

Here are the make percentages of all of the golfers and rounds I examined. I normalized the data to reflect the projected make probabilities from 10 feet, as well as how the normalized data works out.

There is a theory that downhill putts are easier to make than uphill putts. The reason is that the force vectors on a downhill putt tend to get the ball breaking toward the hole. With uphill putts, the force vectors tend to get the ball breaking away from the hole. My research refutes this theory to a degree. The make percentages are significantly higher on uphill putts, however; the second-highest make percentage location is at the 12 o’clock position (straight downhill).

My conclusion is that the downhill straight putt is very easy to make, but once the putt gets away from the 12 o’clock position it becomes increasingly more difficult to make. In summation, the more a putt breaks the more difficult it is to make — and uphill putts will break less than downhill putts.

Lastly, the players (all right-handed putters) had a slight bias in right-to-left putts versus left-to-right putts. This has been a common theory for as long as I can remember, and it held up to be true. The difference in make percentage, however, may be smaller than many people think it should be.

Break Biases and Putting Skill

The research showed a very strong trend in a player’s bias toward right-to-left or left-to-right breaking putts depending on their skill. I labeled golfers in the following categories:

1. Greatest Putter (Upper 90th Percentile in Putts Gained or roughly top-20 in Putts Gained)
2. Worst Putter (Lower 10th Percentile in Putts Gained or roughly ranking 170th or worse in Putts Gained)
3. Good Putter (ranking roughly 30th to 70th in Putts Gained)
4. Mediocre Putter (ranking roughly 120th to 160th in Putts Gained)
5. Average Putter (ranking roughly 80th to 105th in Putts Gained)

I found that the vast majority of the players I analyzed had a significant bias toward either right-to-left or left-to-right breaking putts. Here’s an example of PGA Tour player Richy Werenski, who finished the year at 0.000 in Putts Gained. He neither gained nor lost strokes to the field for the entire season with his putter.

Werenski had a clear bias toward right-to-left putts (40.7 percent) versus left-to-right putts (33.7 percent). Just because a player was putting right-handed, however, did not mean the player would automatically have a bias toward right-to-left putts.

Here’s a breakdown of Rory McIlroy’s make probabilities on the Fall Line Clock.

Outside of the 11 o’clock versus the 1 o’clock position, McIlroy had a bias toward making left-to-right putts versus the corresponding location that broke right-to-left.

As it turns out, the putters that did not have a bias were from the “Greatest Putters” group. They had no significant bias toward leftward or rightward breaking putts. Mackenzie Hughes was a good example of this, as he finished 8th in Putts Gained. Not only did he make a high percentage of putts from most locations on the Fall Line Clock, but he did not have a significant bias toward rightward or leftward breaking putts.

Out of all of the players I researched, making putts at 12 o’clock (straight-downhill), 6 o’clock (straight uphill) and 5 o’clock (uphill, breaks left) were consistently the putts with some of the highest make percentages out of all the Fall Line locations. The only players that could struggle to reach the normalized make percentage average of 38 percent from 10 feet from those locations were the “Worst Putters.” It was not always the case with some of the Worst Putters, but there was a segment of the population that could struggle to make those putts.

One of the conclusions I derived from this was that good putting is not necessarily about holing putts. It is fairly easy for better players to make relatively straight putts, and sometimes in a round the golfer may just happen to get a lot of putts that are fairly straight. On the other hand, the golfer may get a lot of breaking putts. That was one of the amazing things about Jim Furyk’s 58 at TPC River Highlands; only two of his putts were not fairly straight. Obviously his ball striking was phenomenal and he holed putts to shoot 58, but there was a certain amount of luck involved in continually getting favorable putt locations.

Break Biases on Performances Outside of Standard Deviation

I wanted to examine the times that golfers putted better or worse than one standard deviation. What are the commonalities when golfers putt significantly better or significantly worse than normal? Golfers that putted one standard deviation worse than their mean in Putts Gained did not have any noticeable change in their putting other than they just putted worse overall. This was particularly the case in breaking putts. The bias remained the same.

Here’s a look at the putting make probabilities from Billy Horschel on average versus the events where his putting was one standard deviation worse than the mean.

The results were different, however, when I examined golfers that putted one standard deviation greater than their mean. Horschel had a bias toward right-to-left breaking putts on his poor putting performances. The bias went away when he putted better than one standard deviation from his norm.

This was common with virtually every player I studied except for the “Greatest Putters” group, as they did not have a bias toward breaking putts to begin with. If they had a bias towards a particular break, they would often putt even better when they putted significantly better than normal. But they made incredible gains on the putts that broke in a direction that caused them problems — to the point that they were putting as well as they did on the breaking putts they preferred and no longer had a bias.

Conclusions

Based on the data we know the following:

• Tour players greatly favor uphill versus downhill putts as a whole.
• The exception was from 12 o’clock (straight-downhill).
• The best location for right-handed-putting Tour players was at 5 o’clock (uphill, slight break to the left).
• The vast majority of Tour players had some sort of bias toward right-to-left or left-to-right breaking putts.
• Not all right-handed-putting Tour players preferred right-to-left putts.
• As a whole, there was a moderate preference toward right-to-left putts from right-handed-putting Tour players.
• The best putters had virtually no bias toward right-to-left or left-to-right breaking putts.
• Virtually all Tour players consistently favored the 5 o’clock, 12 o’clock and 6 o’clock positions.
• The only Tour players that struggled with straight putts (6 or 12 o’clock) were in the “Worst Putters” category.
• Break bias disappears for a Tour player when they putt one standard deviation better than their mean in Putts Gained.
• Break bias is still present when the Tour player putts one standard deviation worse than their mean in Putts Gained.

For the non-Tour golfer, the data suggests that initial practice on putting should be done on straight putts. The only players I studied that did not do well on straight putts on occasion were the worst putters on Tour. While there has been debate as to how well Tour players putt in relation to the entire world’s golf population, I still tend to believe that even the worst putters on Tour are likely better than any segment of amateur golfers. Thus, if the worst putters of the Tour population can struggle with the straight putts, there’s a strong likelihood that amateur golfers will need to work on straight putts first in order to make a significant improvement in their putting over time.

Once straight putting develops, I recommend that golfers determine how well they putt on right-to-left versus left-to-right breaking putts and see if they have a bias toward a particularly type of break. I recommend that they try to hit putts from various distances and locations between 2 to 4 o’clock (right-to-left) versus 8 to 10 o’clock (left-to-right). It would be best to putt one ball from one side of the hole and then putt the next ball from the opposite side in order to truly determine bias.

Once bias is determined, I would recommend seeking instruction to determine what may be causing the bias against a particular breaking putt. Work on your green reading, stroke mechanics and speed/touch to improve your ability to make more putts from your weak side of the cup. Once you can become a stable putter on uphill putts and erase the bias on breaking putts, you will see much better results and more consistency in your ability to make putts on the course.