Bleeding the Clock in the NBA¶

Clock management receives much attention towards the end of close NBA games, but relatively little outside of crunch time. To some extent, this makes sense. The final minutes and seconds of close games are, by definition, the highest leverage moments of the game and clock management accordingly takes on more importance. However, this doesn't negate the usefulness of sound clock management throughout the rest of a game. In the NBA and other levels of basketball, many of these tactics, such as the 2-for-1 or using fouls to give, are now commonplace.

This year, one relatively less common tactic has popped up across the league and it arises from the intersection of two rules. Per NBA Rule 5-V-b, the game clock only stops following a made field goal during the final minute of the first, second, and third quarters and during the last two minutes of the fourth quarter and any overtime periods. Additionally, Rule 6-I-b states that "on a throw-in, the shot clock shall start when the ball is legally touched on the court by a player." These two rules combine to result in the game clock continuing to run after a made field goal during the noted times, during which the shot clock stands still. This allows teams leading the game to bleed time off of the game clock while maintaining their lead and, therefore, increasing their chances of winning the game as a result.

Notable Examples¶

The Celtics serve as the poster child for the "bleeding the clock" (BTC) tactic thus far this season (not to mention the postseason last year). To illustrate how this plays out in a game, the following clip shows the Celtics rolling the ball after a three-point field goal by the Raptors during a game earlier this year. The shot goes in at 7:16 on the game clock and the Celtics proceed to roll the ball and use screeners to bleed the clock all the way to the 6:56 mark. To add insult to injury, Jaylen Brown promptly sinks a three-point field goal with 6:45 remaining.

This article details the Celtics deploying the tactic during three early games this season. The first cited example occurred with the Celtics leading the Nuggets by 13 points with a little over five minutes remaining and resulted in a flagrant foul by Aaron Gordon after he grew frustrated by the tactic. The Celtics then leveraged the tactic twice to drain about 30 seconds from the game clock while holding onto a single-digit lead against the Heat. And the referees actually erred in blowing the whistle as they bled the clock against the Magic in a similar fashion. The Celtics aren't alone here, as this article describes Ja Morant and the Grizzlies bleeding the clock against the Nets this season.

But whether the use of the BTC tactic extends beyond these two teams or has a meaningful impact on winning games both remain open questions. The following leverages play-by-play data to examine the tactic's distribution across teams and overall impact on win probability.

"Bleeding The Clock" Definition¶

Settling on a definition for the BTC tactic serves as a natural first step. While a team can bleed the clock in the windows described above, let's examine plays following an opponent's made field goal when:

The game is in the fourth quarter or an overtime period, and
The game clock has more than 2:00 remaining, and
The opponent is trailing by three or more points following the made field goal.

Additionally, field goals that occur at the same time as a defensive foul or timeout are excluded as the tactic cannot be leveraged after such events. The dataset contains all 2022-23 NBA regular season games through Christmas day. Here's an example qualifying play from the play-by-play file:

This play meets the definition above for the Celtics. The 76ers make a two-point field goal in the fourth quarter, cutting their deficit to six points. However, the Celtics don't bleed the clock here and immediately grab the in-bound pass to move up the floor.

Tactic Usage By Team¶

With a working definition for the BTC tactic, the following examines its use across the league. The figure below shows the distribution of the time between an opponent's made field goal and the subsequent game event following that field goal. This value represents the amount of time bled (if any) plus the time used during the course of the possession after the shot clock starts. Unfortunately, the granularity of public play-by-play data does not allow one to isolate the time bled directly by this tactic, but this measure serves as a suitable proxy. Each team's distribution of time is overlayed with a dashed line indicating the mean value for that team, while the entire figure is overlayed with a dashed line indicating the mean value across the entire league.

The mean values of time used on possessions following qualified made field goals range from 15.7 seconds for the Kings to 20.5 seconds for the Nuggets, and the Celtics having the third highest mean value matches expectations. Of course, these possessions don't all include examples of teams leveraging the BTC tactic, as the Celtics video above shows. Teams sometimes move quickly to transition up the floor prior to the defense getting set or defenses might pressure the in-bound pass. But the upper tails of these distributions probably contain some bonafide uses of the tactic. Indeed, the play in the Tweet linked above shows up as the Celtics play with the most time bled from the clock this season.

Win Probability Added¶

The above demonstrates that teams leverage the BTC tactic to varying degrees, but does not demonstrate how much it impacts winning. The most direct way to approximate how much value teams derive from this tactic is to examine the difference in win probability before and after its use.

Win probability models have many applications in the game and inpredictable has likely the best-performing public version. The site even has a calculator so users can examine the effect of time remaining, score differential, and possession on the probability that a team will ultimately win a game.

To examine the value added from bleeding the clock, the following leverages a win probability model constructed from play-by-play data covering the 2017-18 through 2020-21 NBA regular seasons using the same inputs as the inpredictable calculator. On a held-out dataset from the 2021-22 NBA regular season, this model performs comparably to the inpredictable and ESPN models, albeit on different held-out datasets.

With this model in hand, the win probability of the team using the BTC tactic can be calculated at the beginning and end of the time window established to create the visualization above. The following figure shows the win probability added from bleeding the clock by team during the 2022-23 NBA regular season thus far.

Well, here the Celtics are again: leading the league in win probability added by way of the BTC tactic and nearly 0.05 win probability points ahead of the Grizzlies, another noted BTC tactician. Of course, the Celtics benefit from often leading in the fourth quarter and being able to use this tactic more often by nature of having the best record in the league. Viewing the above on a rate basis would identify the teams leveraging the tactic most often per opportunity, but the raw total win probability values show the degree to which teams can benefit, with the Celtics adding more than 0.4 wins by simply bleeding the clock.

Now, let's go back to an example from the article highlighting the Celtics' use of the BTC tactic and assess the impact on win probability.

After the Jimmy Butler dunk at 4:12 on the game clock, Malcolm Brogdon takes his time retrieving the ball and slowly rolls the ball into play towards Marcus Smart, who picks it up at the 3:58 mark. The ensuing possession eats up 23 total seconds, resulting in an increase of 1.7 percentage points of win probability for the Celtics due to the game clock alone.

While this may seem small, the above figure shows that these plays can add up to an appreciable amount of win probability added throughout a season. In a league where one game can mean the difference between home court advantage or missing the playoffs, teams should consider bleeding the clock whenever an opportune situation presents itself.