Oklahoma City Thunder guard Russell Westbrook is poised to break the NBA record for triple-doubles in a season. (Sue Ogrocki/AP Photo)

Russell Westbrook continued his historic season on Tuesday night — 12 points, 13 rebounds and 13 assists — in the Oklahoma City Thunder’s 110-79 win over the Milwaukee Bucks. It was Westbrook’s 41st triple-double of the season, tying Oscar Robertson’s 55-year-old NBA record for the most triple-doubles ever in one season.

But before we start uttering both names in the same sentence, it’s worthwhile comparing their seasons head-to-head.

For starters, Robertson was a slightly more efficient shooter (47.8 effective field goal percentage) than Westbrook (47.4 percent) without the added benefit of the three-point line, introduced in 1979. Plus he grabbed more rebounds and dished out more assists per game. Westbrook, meanwhile, is producing his triple-doubles despite playing almost 10 minutes fewer per night, making his overall numbers extraordinary in terms of rate of production.

Yet Westbrook’s apparent domination of the league this season is not as impressive as it seems.

Triple-doubles have exploded in frequency in recent years. There were just 42 during the 2012-13 season, less than half as many as during the current campaign (110 and counting). Even without Westbrook’s record-setting pace, there would still be almost two-thirds more triple-doubles as there were just four seasons ago.

Westbrook’s triple-doubles are also inflated by his ability to grab uncontested rebounds.

A guard typically doesn’t play close to the hoop, but Westbrook has always been a solid rebounder for a guard. Still, this season Westbrook is on another level, grabbing 17.1 percent of his team’s available rebounds, the highest for a guard qualifying for the scoring title since 1981-82, when Magic Johnson grabbed “only” 13.7 percent of the rebounds for the Los Angeles Lakers.

The key? Westbrook has done it by leading the league in uncontested defensive rebounds per game (7.9) with the lowest contested defensive rebound percentage among any player grabbing at least five rebounds per game. In other words, a very high share of his total rebounds come without having to win a battle for a loose ball. The Thunder also frequently concede rebounds off missed free throws to Westbrook, thus further padding his stats.

To be fair, this appears to be by design rather than selfishness on Westbrook’s part.

“No one cares. We’d rather it be him [getting the rebound],” Steven Adams told ESPN’s Royce Young in December. “I like it because I can actually box out my dude. It’s good that he actually gets to come in and take it. I don’t mind it.”

The benefit is getting the ball into Westbrook’s hand as quickly as possible, but his individual production in transition is below average (0.98 points per possession, bottom 30 percent of the NBA) with just 30 percent of his transition opportunities leading to an assist. Almost a quarter of his transition possessions as the ballhandler end up in a turnover (23.1 percent), the fourth-highest among guards with at least 100 possessions.

And then there’s his defense, which can be described as lackluster.

Westbrook contests 3.6 shots per game, the lowest rate of any player averaging at least 30 minutes per night. The players he guards attempt eight field goals per game, per Synergy Sports, which means they take more than half of their shots without any sort of defensive effort on Westbrook’s part despite him being the closest defender. Even his attempts to contest shots does little good: Opponents have a better field goal percentage on shots he defends (48.6 percent) than on all of their other field goal attempts combined during the regular season (45.2 percent).

Westbrook’s defensive deficiencies are typically the result of being out of position. As a point guard, you’d expect Westbrook to be responsible for the opposing point guard, yet Westbrook is often too far away to make any meaningful contribution on defense. On one play in the second period against Charlotte, Westbrook’s attention is fixated on Nicolas Batum during a pick and roll, leaving Hornets point guard Kemba Walker (green arrow) all alone behind the three-point line. Batum would connect on a cross-court pass to Walker, who made the one-dribble jumper from behind the arc.

Westbrook also has trouble with spot-up shooters, particularly when they drive to the basket or attempt a catch-and-shoot. In fact, opponents score almost as much when Westbrook is classified as the closest defender on catch and shoots (1.1 points per shot) as they do when the NBA classifies them as unguarded (1.3), like when San Antonio Spurs’ LaMarcus Aldridge was able to find Manu Ginobili open on the perimeter out of the post.

Every player gets caught flat-footed, and before you think we’re just cherry-picking those two possessions, consider that Westbrook ranks in the bottom 20 percent or worse on defense against jump shots (52.9 effective field goal percentage against) and three-point shots (1.26 points per shot allowed). Even his steals are down, with his 2.3 steals per 100 possessions his lowest rate since the 2009-10 season.

It’s likely only a matter of time before Westbrook has the most triple-doubles in NBA history, but in today’s scoring environment, coupled with a lack of meaningful rebounds and spotty defensive effort, it looks more impressive than it is.