On Sunday night in Charlotte, Rajon Rondo scored 20 points and handed out 16 assists in a 94-82 Celtics victory over the Bobcats. Rondo’s line didn’t even seem that unusual -- he’s handed out double-digit assists in 22 straight games, the longest run since John Stockton’s 29 in 1992 -- but it was the circumstances that gave it added weight.

Rondo was playing without Ray Allen, Paul Pierce or Kevin Garnett, and instead found himself in the starting lineup with four players who were slotted for bench duty when the season began. Only one -- Brandon Bass -- was even in the rotation back on Christmas Day. True, it came against the woeful Bobcats, but Rondo was matched up with D.J. Augustin, a fourth-year guard who has been a solid, if unspectacular, player since he arrived in the league.

Rondo’s play was critical for a team that is still fighting for playoff positioning. They had fallen behind Atlanta in the race for homecourt advantage in the first round, and another loss would have been damaging. If the Celtics were going to win the game, Rondo would have to be engaged and dynamic. He was. Rondo was not just looking for teammates as a facilitator, he was aggressively looking to score, something coach Doc Rivers has wanted him to do all season.  

It was some validation that Rondo is not just a creation of The Big Three, a fortunate guard who found himself in a perfect situation to rack up assists. Of course, it can also be argued that Rondo’s skill-set blends perfectly with his veteran teammates because of his pass-first mentality and their ability to make jump shots. 

All of that is important because context is crucial when talking about NBA players and their performances. That’s true of both our observations and the statistics we use to quantify how well, or not, someone is playing. In particular, Rondo is not an easy player to quantify. He has been amassing huge numbers and in typical Rondo style, he’s done them in over the top fashion.

He’s recorded 303 assists in the last 22 games, which has vaulted him ahead of Steve Nash for the highest per-game average. His impressive streak aside, Rondo isn’t a consistent machine like Nash. Rather his specialty is make-your-jaw-drop performances that leaving you scrambling for historic comparisons. Case in point: He has six triple doubles this season. Nine other players are tied for second with one.

And yet, by other measures, Rondo grades out as a good, but not elite point guard. Among point guards who play more than 30 minutes a night, Rondo ranks 14th in John Hollinger’s Player Efficiency Rating (PER) behind players like Jarrett Jack, Ty Lawson and Brandon Jennings.

For some that’s proof that advanced numbers are meaningless. For others, it’s an invitation to find out why Rondo ranks so low and the answer is fairly obvious: He’s not a very good shooter. His true shooting percentage (which accounts for two’s, three’s and free throws) is just over 48 percent, ranking him next to last among point guards who play more than 30 minutes a night. He also turns it over at a higher rate than any other comparable point guard in the league after Nash.

(Fun aside: Are turnovers overrated? Answer: sometimes).

Hollinger’s PER is a total derived from a formula that calculates numbers found in the box score. It’s a tool, not the end-all and be-all of statistical basketball analysis. Given Rondo’s less-than-stellar shooting numbers and his high amount of turnovers, it’s no surprise that he doesn’t grade out among the league’s best in that particular statistic.

But he has to be doing something right. We know that simply by A) watching him play and B) the team’s 21-8 record since the All-Star break. His numbers don’t tend to him do justice, even when they enter sublime territory, like his assist streak.

“Well, that’s phenomenal,” Rivers said last week after the streak reached 19 games. “Honestly, I don’t even know what that means. I know it means that he’s playing vey well, but I don’t need the numbers to tell me that is what I’m trying to say.”

Rivers often says that he never looks at Rondo’s numbers because if the team plays well, that’s usually a reflection of his point guard. The same holds true if it doesn’t. For his part, Rondo has no use for numbers. “It means guys are putting the ball in the hole,” he said nonchalantly when asked about his assists recently.

But advanced metrics aren’t just about counting up numbers found in the box score. We also have more-developed plus-minus data that can help tell us a player’s impact when he’s on -- and just as importantly -- when he’s off the court.

The Celtics score 102.8 points per 100 possessions when Rondo’s in the game, a figure that would move them move from awful -- where they are now -- to merely mediocre. But when Rondo leaves the game, their offensive production tumbles all the way down to 95 points per 100 possessions, which is catastrophically bad. It’s worse than the Bobcats, for example.

The Celtics are 7.74 points better on offense when Rondo is in the game than when he’s out, a number that ranks seventh among point guards who have played more than 1,000 minutes behind players like Sacramento rookie Isaiah Thomas and Portland’s maligned Ray Felton.

That doesn’t mean that Rondo isn’t as good as those players, obviously. It’s a number that is completely dependent on team context, and on the Celtics the only player who has a greater impact on points per possession is Kevin Garnett. (Garnett’s total on/off differential including defense is 11.58 points per 100 possessions, which ranks ninth in the NBA for players with more than 1,000 minutes played. That’s one of the reasons he’s a more viable MVP candidate than Rondo whose 5.78 point-differential ranks a distant second).

Still, all this data explains some -- but not all -- of Rondo’s importance to the Celtics. During his streak, Rondo has 303 assists, an average of almost 14 a game. The Celtics have made 837 shots during the stretch, so Rondo has assisted on more than a third of their made shots during this run. Adding further context, Rondo has had a hand in over 50 percent of the team’s assists while he was on the floor this season.

That’s important because no team relies on assists more than the Celtics when it comes to making shots. Over 67 percent of their made field goals come via an assist and Rondo is the player who is most responsible for delivering the ball. Of his 11.6 assists per game, more than four per game lead to baskets at the rim, which ranks second behind Nash and 3.8 lead to jump shots from between 16 and 23 feet, the most in the league.

Some people tend to discount the number of Rondo passes that lead to long jumpers, but that’s the way the Celtics play. In Garnett and Bass, they have two of the best long-range shooting big men in the league, not to mention Pierce and Allen. Can you have one without the other? Rondo’s offensive differential when he’s out of the game suggests that they can’t.

Would Rondo’s huge assist numbers take a plunge without the Big Three? Maybe, but it’s worth pointing out that against the Bobcats, six of his assists led to shots at the rim and six led to long jump shots. Rondo didn’t change, even if the personnel on the floor did.

It’s pure speculation how he’d do without the three future Hall of Famers because he’s never had to do it before. While Rondo may complement them perfectly, having players who could run the court with him remains an intriguing open-ended possibility for the future.

Even with all that, there’s no advanced metrics for Rondo’s uncanny ability to thread passes where only his target can catch them. There’s no degree of difficulty meter for the layups that he kisses high off the glass like a hustler running a pool table. All we’re left with is some context for a player who lies just far enough outside the long each of advanced stats to occupy a unique place in the game.