How Do Rebound Shots Impact Shooting Percentages?

I've written a number of pieces on this site quantifying the value of different kinds of shots, but admittedly there has been one aspect of shot success missing from the analysis. A shot attempt can result in a block, a miss, a shot, or a goal, but it can also result in a subsequent shot: a rebound shot. If certain kinds of shots are more likely to produce rebounds than other kinds, that can change the equation in terms of the success rate of those shots. 

I took a look at three different rebound rates for different kinds of shots. The first is a loose puck rate, or the inverse of the rate at which the goalie freezes the puck. If a player gets a shot on goal and there isn't a faceoff in the three seconds following that shot, then it qualifies as a loose puck result. Overall approximately 75 percent of power play shots result in loose pucks.

Secondly, I looked at the percentage of shots on goal for each category that lead to rebound shot attempts. Essentially, these were shots of high enough quality that the goalie couldn't steer a rebound to a safe place. Overall, approximately 13 percent of power play shots result in rebound attempts at the goal.

Finally, I explored the percentage of shots on goal that led to rebound goals. This could have meant an immediate rebound goal or a series of rebound shots that eventually resulted in the puck being jammed in. The sample for this was bound to be small (29 rebound goals in total among the six teams I've tracked); the percentage came in at 0.18 percent. I will note that this double-counts a few goals since both the rebound and original shot can be marked as leading to a rebound goal if there is more than one rebound, but I felt that this was still the best way to go about it to get a good sense of the effectiveness at quality rebound generation for different types of shots.

Here, 'SC' means a shot from the scoring chance/home plate area, 'RR' means a shot from a one-timer that crosses the Royal Road center line, and 'OT' means a one-timer in general. Anything with an 'n' in front indicates that the category doesn't have that characteristic.

It's tough to glean too much from the first set of categories. One-Timers that don't cross the royal road appear to generate rebounds slightly more often than non one-timer shots, but otherwise the sample of royal road one-timers may be too small to properly evaluate. It doesn't make sense to me that those shots would lead to fewer dangerous rebounds when they get on goal (that's the challenge), so I'm not sure what to make of that other than a sample size issue.

Moving on, despite moderate sample sizes, shots taken with a player in front of the net lead to significantly more loose pucks and rebound attempts. I've been emphasizing since I began tracking screens halfway through the season how important they are, and this lends more evidence to support that claim.

Note: To clarify those categories, I have been tracking tipped shots since the beginning of the year, so I can separate my entire 1649 shot sample into tipped and not-tipped shots. For screens, however, I only have 485 shots in which I know for sure whether there was a screen. So the 'Clear Sight' category are shots where there definitely was not a player in front of the net.

I decided to compare slap and wrist shots in low danger situations because it is in those circumstances where players often have a choice between the two. The difference appears negligible in terms of rebound generation on that front. One-Timers aren't included in that analysis.

Finally, rebounds don't lead to loose pucks all that often according to these numbers, but remember that the loose puck category is occasions where there isn't a faceoff within three seconds. There are occasions where a rebound shot can lead to another rebound shot and then a faceoff but it wouldn't be counted as a loose puck result if it happens in less than three seconds. 

So how can we use these numbers to better inform the idea of shooting percentage? Since screens and tips appear to most significantly affect rebound percentages, let's look at those categories and adapt shooting percentages as a result.

Clearsighted shot attempts go in the net on the power play 4.94 percent of the time (all according to my six-team data), with 51 percent of those attempts going on net. If we take 100 clearsighted shots therefore, approximately five will go in the net and 45 others will be saved by the goalie. According to the numbers in the above table, those 45 will produce approximately 5.5 rebound attempts. The average rebound Corsi shooting percentage on the power play according to my data is 12 percent, so that means an additional 0.66 goals. On top of that two-thirds of a goal, those 5.5 attempts will lead to about one secondary rebound-attempt, which is on average another 0.12 goals. Put that all together, and Corsi shooting percentage on clearsighted shots goes up from 4.94 percent to 5.72 percent.

Now what about screened shots? They go in 5.81 percent of the time, with 41 percent going on net (it's not a coincidence that this percentage is lower since there's another man in front who could block it). So out of 100 shots, six go in the net, and another 35 are saved. Those 35 produce about 6.5 rebound attempts and 1.1 secondary rebound attempts, meaning that true Corsi shooting percentage is not 5.81 percent but 6.74 percent.

Finally, tipped shots go in 14.47 percent of the time, with 56 percent going on net (if it's blocked before reaching the goal-mouth it's unlikely to have been tipped, which explains the difference here). On 100 shot attempts, approximately 14.5 go in, and 41.5 others go on net. These produce about 7.5 primary rebound attempts and 1.25 secondary rebound attempts. Adding that all together, Corsi shooting percentage increases from 14.47 percent to 15.52 percent, the biggest jump of the three. You can see those numbers presented in the table below, with the differences measured in percentage points.

The sample size for tipped shots is obviously small, but you can see how effective putting a man in front of the net can be, with those shots overall going in or leading to rebound goals approximately 8.26 percent of the time, compared to 5.72 for clear shots, or almost 45% more often.

Having a goal-line player who can provide a consistent screen, like the Philadelphia Flyers and New York Islanders have with Wayne Simmonds and Anders Lee, can be a huge advantage. It's the coach's job to put those players in the right spots on the ice, and craft entry and in-zone schemes to create screen and tip shot opportunities.