The Boston Celtics continued their remarkable winning streak Friday night, stretching it to seven games with an 18-point comeback on the road against the Oklahoma City Thunder. Leading the way was Kyrie Irving, who scored 22 of his 25 points in the second half, including 13 in the fourth quarter alone.

Perhaps the biggest play of the game came from Irving with a little over four minutes remaining. After getting fouled on a 3-pointer, Irving stepped to the line to complete the four-point play. Instead, his free throw ricocheted off the back of the rim and straight back to him. Before the Thunder knew what was happening, Irving put in a layup to turn it into a five-point play.

The five-point possession pushed the Celtics' lead from one point to six points, and they never trailed again, holding on for an impressive victory that improved their league-best record to 7-2.

At first, you might just think, "ah, bad luck for the Thunder." A fluky offensive rebound really cost them in a close game. However, upon further inspection, it might not have been so fluky, after all. Yes, it was an unfortunate bounce straight back to Irving, but OKC's strategy on free throw rebounds was also partially to blame.

During Russell Westbrook's triple-double campaign last season, one of the criticisms was that other players on the Thunder let him grab rebounds they could have gotten so that he could pad his stats. One place this is especially true was at the free throw line, where OKC's two low players just sort of back their opponents up, and Westbrook swoops in for the board. 

This season, again, they are employing that strategy. Let's watch Irving's rebound again, and you can see this in action: 

As the shot by Irving goes up, Steven Adams and Carmelo Anthony casually move slightly backwards to try and keep the Celtics they're matched up with on their backs, but make no effort whatsoever to get the ball.

Adams and Anthony stand flat-footed, waiting for Westbrook to go in for the board.

When the ball bounces straight back to Irving, however, the Thunder are stuck. Westbrook had sauntered into the middle of the lane, but without making an attempt to box out Irving, while Adams and Anthony are standing flat-footed. And with neither Ray Felton nor Paul George pinching down quick enough, Irving gets the rebound. 

The ball doesn't bounce quite where the Thunder want it to, and they're left stranded as Irving gets a crucial board. 

Then, in part because Adams is just hanging out and not expecting to do anything, he's in no position to contest Irving's follow-up layup.

Now, did the Celtics get some luck with the ball going straight back to Irving? Certainly. However, as you can see, the Thunder's strategy was at least partially to blame. Adams and Anthony mostly take themselves out of the play, and Westbrook doesn't make an attempt to box out anyone, leaving that job to his teammates at the top of the key, even though the shooter is usually the responsibility of the player in Westbrook's position. 

This part of their strategy is the main reason why Irving got the clutch rebound. If Westbrook jumps in front of Irving to box him out instead of walking down near the rim, it's likely he can get in front of the Celtics point guard and grab the ball.

The thing is, most of the time, this strategy is no problem for OKC. Teams usually don't crash the glass hard on free throws, and the ball usually doesn't bounce straight back like it did this time with Irving. 

Here's another example from this season where this setup works out just fine. Again, Adams and Jerami Grant just back their matchups up, while Westbrook focuses solely on the ball, and George pinches in to get the shooter: 

Now, to be fair to Westbrook and the Thunder, this is not purely a selfish thing. There are reasons why it makes sense to let Westbrook grab some of these rebounds, as he can then just take the ball up himself, and sometimes jumpstart their fastbreak. 

However, especially on free throw situations late in close games, it's fair to wonder if the Thunder should start employing a more conventional and conservative style. Doing so might not have guaranteed they get the rebound on this specific play with Irving and the Celtics, but it would have given them a better chance.