Before the Philadelphia Flyers went on their surprise run towards the playoffs, the emergence of Shayne Gostisbehere was the no-brainer choice for the most exciting story of their season. Viewed by most scouts as an intriguing yet flawed prospect coming off a major knee injury, expectations were relatively low surrounding the 22-year old defenseman at the start of the year, especially after he failed to make the Flyers' opening night roster.

Gostisbehere finally got his shot to make an impact at the NHL level in mid-November, and has been a key player ever since. His 43 points (16 goals, 27 assists) lead all rookie defensemen, and his 2.16 Points per sixty minutes of overall ice time is tops among all NHL blueliners this season. In addition, his elite skating ability and blistering slapshot has made him a staple on national highlight shows, helping the "Ghost Bear" phenomenon to spread from Philadelphia to the entire hockey world.

But as Gostisbehere's rookie season comes to an end and analysts are making their preferences for the Calder Trophy (given to the league's top rookie) known, one key argument against the Flyers' defenseman is beginning to appear. Despite all of Gostisbehere's points and highlights, his season-long advanced statistics are nothing special.

With five games remaining, he currently sits on a 49.4% Corsi For percentage, and a -1.3% Corsi relative to his teammates. This means that Philadelphia not only has narrowly lost the overall shot attempts battle with Gostisbehere on the ice, the Flyers actually perform a bit better from a play driving standpoint with the young defenseman on the bench.

It's tough to reconcile these metrics with the eye test, because Gostisbehere certainly looks the part of an electrifying, possession-driving defenseman. Still, the numbers state otherwise, and they cannot be ignored. If Gostisbehere is really a true talent negative Corsi player, then his Calder case does take a serious hit. More importantly, the mediocre advanced metrics present a more pressing concern -- what if Shayne Gostisbehere is simply not a play-driver, and isn't the future star that he appears to be? Let's take a deep dive into the contextual metrics to see if that case holds water.

Microstats love Shayne Gostisbehere

Over the course of the 2015-16 season, I've made an attempt to manually track every time that the Philadelphia Flyers enter the offensive zone during 5-on-5 play, and each time a Flyers opponent does the same. In addition, I'm also tracking Flyers exits from the defensive zone, distinguishing between controlled exits, uncontrolled exits, turnovers, and in-zone passes.

Using this data, it becomes possible to isolate three key skills of all Flyers' defensemen -- zone exit efficiency, the ability to create offensive zone entries on the attack, and also to deny them while defending against the rush. All three skills would seem to help push the puck in the right direction, leading to more attack time, more shots and more goals for the defenseman's team.

Shayne Gostisbehere excels in all three areas. In fact, he's the best Flyers defenseman in each of the key microstat categories.

Defenseman Entries Per 60 Controlled Exit Percentage (accurate as of 1/27) Controlled Entry Percentage Allowed Shayne Gostisbehere 12.23 (1st) 27.47% (1st) 44.69% (1st) Michael Del Zotto 8.93 (2nd) 24.97% (2nd) 53.18% (5th) Evgeny Medvedev 8.61 (3rd) 23.31% (3rd) 50.16% (3rd) Brandon Manning 8.53 (4th) 21.92% (4th) 49.40% (2nd) Mark Streit 8.14 (5th) 21.09% (5th) 52.72% (4th) Radko Gudas 6.71 (6th) 16.23% (6th) 53.42% (6th) Nick Schultz 6.62 (7th) 16.07% (7th) 58.06% (7th)

First, let's start with offensive zone entries. Gostisbehere leads all Philadelphia blueliners in Entries per 60 with 12.23, and he also has the highest controlled zone entry percentage on the defense, checking in at 46.55 percent. Essentially, Ghost both creates more entries than his peers and has the highest rate of entries with possession of the puck -- the most valuable type. The rookie defenseman has done more to help create scoring opportunities than any other Philadelphia blueliner.

Gostisbehere also has proven effective at preventing opposing forwards from generating controlled zone entries of their own. When directly targeted on the rush by opponents, Ghost has allowed them to enter the Flyers' end with possession of the puck just 44.69% of the time. The next best Flyers defenseman at preventing controlled zone entries is Brandon Manning, who checks in at 49.40%, almost five full percentage points behind Gostisbehere.

Since controlled zone entries generated a league-average of 0.66 unblocked shot attempts in 2013-14 while uncontrolled entries were worth just 0.29, there is definite value in directly forcing opposing forwards to play dump-and-chase hockey. At least in his rookie season, Gostisbehere has shown an ability to do just that.

Finally, Gostisbehere has been very effective in engineering defensive zone exits with possession of the puck. 27.47 percent of his defensive zone touches (as of January 27th) resulted in the Flyers leaving their own zone with possession -- another defense-leading mark. Controlled zone exits qualify both as strong defensive plays (gets the puck out of danger) and offense-creating plays, since it it usually marks the start of a transition up ice.

Shayne Gostisbehere is a microstat tracker's dream defenseman -- adept in creating offense with the puck and intelligently aggressive without it.

Do defensemen with strong microstats make good possession defensemen?

All the great entry and exit metrics in the world are meaningless unless they help a defenseman to drive play and aid his team in scoring more goals than the opposition. After all, Radko Gudas does not grade out as particularly strong in the microstats, and he's still been Philadelphia's best play-driving defenseman this season.

Still, it's undeniably impressive that Gostisbehere rates so high relative to his teammates in entry creation, entry defense, and exit efficiency. The metrics appear to show that the Flyers' rookie is taking a very active role in pushing the puck in the right direction, and it would make sense that defensemen who pace their teams in these categories tend to drive possession better than less active teammates.

Let's test that theory. While my 2015-16 season data is limited to the Philadelphia Flyers, we can use Corey Sznajder's work on the All Three Zones project during the 2013-14 season to see if defensemen who rank highly on their teams in microstatistics tend to be above-average play-drivers. Corey tracked entries per 60, controlled exit percentage, and entry defense for each NHL player during that season, giving us a very large dataset.

We're looking for defensemen who excelled in all three categories relative to their teammates, and also received lots of playing time. To that end, let's only evaluate defensemen in 2013-14 who ranked in the top-seven on their teams in overall 5-on-5 ice time. Then, we'll look at only those who rank at least in the top-three among their team's blueliners in entries generated (Entries/60), controlled exit percentage, and controlled entry percentage allowed. Finally, we can look up each player's Corsi Relative to see if the strong microstat performance translated to above-average possession play.

The results are unsurprising. Defensemen who are efficient at engineering controlled zone exits, creating offensive zone entries, and preventing opponents from getting in on the attack with control of the puck almost always did a better job of driving play than their teammates.

Of the 27 defensemen in 2013-14 with no holes in their microstatistical performance, 24 of them finished with positive relative possession metrics in that season. The median performance was a perfectly-solid +2.65%, posted by Toronto's Cody Franson.

This doesn't mean that Shayne Gostisbehere is destined to be a positive possession player. Justin Schultz (last on this list) is actually an intriguing low-end comparison for the Flyers' rookie, as he is above-average with the puck on his stick but tends to struggle in defensive zone coverage, limiting his overall effectiveness. But there's also a number of positive comparisons here that hold up from an eye test scouting perspective. Matt Niskanen, James Wisniewski, Mike Green and Brian Campbell are all offensively-gifted defensemen who have driven possession regularly in their careers, and are reasonable projections for Gostisbehere's eventual ceiling.

The strong statistics on this list imply that Gostisbehere's mix of puck-carrying ability, breakout proficiency, and aggressiveness in the neutral zone usually results in an above-average play driving defenseman. It seems like Gostisbehere's process on the ice is sound. So why haven't the results been there?

The Andrew MacDonald effect

When we analyzed Shayne Gostisbehere's statistical case for the Calder Trophy back on February 15th, the defenseman was solidly positive by advanced shot attempt differential metrics like Corsi. His +1.54% Corsi Relative sat around the 70% percentile among NHL defenseman, right in line with main competition Artemi Panarin's rank among his forward peers.

Unfortunately for Gostisbehere, his metrics began a steady slide around the time that article was posted, all the way to his current underwhelming -1.30% Corsi Rel. Interestingly enough, it was also mid-February when the Flyers made a major roster move that greatly affected Gostisbehere.

Prior to February 14th, Gostisbehere had spent most of his even strength ice time paired with one of Brandon Manning, Evgeny Medvedev, or Michael Del Zotto. But after Del Zotto suffered a wrist injury against the New Jersey Devils on February 13th, the Flyers chose to call up Andrew MacDonald from the AHL, where he had languished for most of the season. Gostisbehere was immediately paired with MacDonald starting on February 14th, and that's when the rookie's advanced metrics began to really dip.

Time Period 5v5 Corsi Relative to Teammates Gostisbehere November 14 - February 13 +1.20% Gostisbehere February 14 - April 3 -5.90%

For those who prefer visuals to understand changes over time, here is a great 10-game rolling Corsi Relative chart from Corsica.Hockey that illustrates the timeframe of Gostisbehere's declining relative possession metrics.

Before being paired with Andrew MacDonald, Shayne Gostisbehere was generally delivering above-average on-ice shot attempt differentials. But as the chart shows, there's a clear dip into the negative right around the midpoint of February -- just as Gostisbehere and MacDonald were paired together. The rookie defenseman has been unable to recover since.

But is it realistic to think that MacDonald could be dragging down Gostisbehere that much? At least from a possession standpoint, it certainly seems possible. Since the start of the 2012-13 season, no defenseman in the NHL who has played at least 2000 5-on-5 minutes has posted a worse Corsi Relative than MacDonald and his negative-5.65%. At least by on-ice shot attempt differential statistics, there's a real case to be made that MacDonald is one of the worst defensemen in the NHL.

Some have argued that metrics like Corsi do not tell the full story when it comes to MacDonald, primarily referencing his high blocked shot totals (though he's still third-worst in the NHL when just looking at unblocked attempt differential) and the fact that he does perform better when looking at on-ice goal-based statistics (he has a far less bad negative-2.90% Goals For Relative over the same time period).

That's an argument worth having. And in truth, if you do believe that Corsi doesn't accurately measure what Andrew MacDonald brings to the table, then you should be even less concerned about Gostisbehere's recent drop in on-ice shot differential, since it's likely being caused by a Corsi-defying player.

Regardless of your opinion on whether Corsi is a good way to judge MacDonald, what is undeniable is that the veteran defenseman regularly posts terrible shot attempt-based results, making it totally feasible that his deficiency in that area could have a major negative effect on the same metrics of his regular partner.

Over the past two months, that partner has been Shayne Gostisbehere, and you see the results.

Conclusion

Shayne Gostisbehere's on-ice shot attempt differentials at 5-on-5 currently sit somewhere between "acceptably mediocre" and "mildly concerning." His 49.45% Corsi For percentage shows that the Flyers get outshot by a small margin with the Ghost Bear on the ice, and his -1.3% Corsi Relative hints that Philadelphia has controlled play better when Gostisbehere is sitting on the bench. Neither are promising signs.

But the eye test tells a different tale, that of a dynamic playmaker who has been a major part of the Flyers' rise to respectability in the season's second half. Manually tracked microstats back up the eye test, showing that Gostisbehere has helped to drive possession via offensive zone entries, controlled defensive zone exits, and by forcing opponents to play dump-and-chase hockey on the rush.

Defensemen that excel in all three areas tend to drive play at a solid rate, as shown by Corey Sznajder's All Three Zones project from 2013-14. So how could Gostisbehere be doing so many things right at the micro level while still struggling in overall possession metrics?

One theory is that his extended time playing alongside Andrew MacDonald has been a major contributor to Gostisbehere's declining advanced metrics. MacDonald has been one of the league's worst defensemen by 5v5 on-ice shot attempt differential for the past four seasons, and Gostisbehere's Corsi dip lines up perfectly with when he was paired with MacDonald in mid-February.

It's fair to argue that Gostisbehere's late season advanced statistical decline hurts his case at the Calder Trophy for best rookie, especially when facing off against tough competition like Artemi Panarin, Connor McDavid, Dylan Larkin and Colton Parayko. After all, on-ice performance is what matters for those awards, not what "could have" or "should have" happened.

But considering Shayne Gostisbehere's wide-ranging skillset, I'd be willing to bet that he won't be a even strength possession liability in future seasons. So long as the Flyers avoid making the Gostisbehere-MacDonald pairing a permanent lineup fixture, their dynamic young defenseman will probably drive play for years to come.

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All statistics courtesy of War-On-Ice.com, Corsica.Hockey, Corey Sznajder's All Three Zones Project, or manually tracked by Charlie O'Connor.