On the verge of the 2015-16 season's halfway point, the Philadelphia Flyers remain in striking distance of a playoff spot. After missing the postseason last year, many league observers referred to the Flyers as a team in a rebuild, but general manager Ron Hextall and first year NHL coach Dave Hakstol have been able to keep their roster out of the cellar and in relative contention.

It was always going to be difficult for the Flyers to bottom out entirely, considering the presence of high-end forwards Claude Giroux and Jakub Voracek. Combine the team's two stars with above-average goaltending from the tandem of Steve Mason and Michal Neuvirth, a leap in performance from young center Sean Couturier, and the jumpstart provided by early-season callup Shayne Gostisbehere, and it's not surprising that Philadelphia remains within playoff striking distance.

But one previous strength has let the Flyers down in the season's first half - the play of their special teams.

Through 40 games, the Flyers' power play ranks 28th in the NHL, and the penalty kill hasn't been much better, slotting in at 25th. That's a huge drop for the PP in particular, which has ranked third, eighth and third over the past three seasons. On the other hand, the Flyers' penalty kill struggled last season in terms of overall efficiency (26th in NHL), and the team has been unable to reverse the trend so far this year.

But raw goal-based efficiency numbers often do not tell the whole story. Because such little time is spent on special teams compared to even strength, the performance of a power play or a penalty kill is subject to wild swings due to bad bounces, one-time mental mistakes, and plain old sensational individual performances.

As a result, when judging special teams performance, it's helpful to also look at shot and scoring chance generation and prevention. Maybe a power play is creating lots of chances, but either consistently runs into hot goaltenders or is just having trouble finishing. And a penalty kill can be doing all the right things - clearing the zone often, keeping most shots to the outside - but look terrible because of poor goaltending.

It turns out that the Philadelphia Flyers may fit the bill on both counts. Not only have the Flyers underperformed relative to their shot/chance metrics on special teams, they have probably been the most unlucky team in the league thus far in 2015-16.

Shot metrics paint a much prettier picture

Thanks to the great people at War-On-Ice.com, there are multiple ways to to view the underlying shot generation and prevention metrics of the Flyers' special teams this year. And each tells a slightly different story.

Fenwick is a measure of all unblocked shot attempts directed at the net, which is useful because it provides a solid proxy for zone time and how many times a power play unit finds an open lane. But good positioning by penalty killers can result in missed shots, so it helps to also look at Shots on Goal as well. However, not all missed shots and shots on goal are quality - some are relatively weak shots from the outside. To account for that, we can count Scoring Chances and High-Danger Scoring Chances, to see if certain power plays have been successful thus far due to their quality of shots rather than pure volume.

By looking at all of these metrics, we can judge if the Flyers' power play and penalty kill truly deserves their low rankings. First, let's look at the power play, analyzing the team's ability to generate shots and chances.

Fenwick For Per 60 Shots on Goal For Per 60 Scoring Chances For Per 60 High-Danger Scoring Chances For Per 60 Flyers 82.4 59.6 56.0 24.1 NHL Rank 5th 3rd 6th 4th

Those rankings actually look pretty good, and certainly don't seem befitting of a power play ranked 28th in the NHL. Most promising is the fact that they rank consistently high across the board. If they were generating lots of shots but not many chances, that could point to a structural issue with the power play. If the shot metrics were low but the scoring chances were high, there would be legitimate concern that Philadelphia's shot quality would be sustainable over the long term.

Instead, the Flyers rank in the top-six in the NHL in each generation category. Now, let's analyze the penalty kill, this time evaluating its ability to prevent shots and scoring chances.

Fenwick Against Per 60 Shots on Goal Against Per 60 Scoring Chances Against Per 60 High-Danger Scoring Chances Against Per 60 Flyers 69.2 52.2 46.8 19.5 NHL Rank 6th 11th 13th 13th

These are a bit more middling, but still far better than their 25th-place ranking in the penalty kill efficiency charts. Philadelphia does a solid job of preventing teams from attempting shots while on the power play, but those shots are more likely to make it through to the goaltender and be of a higher quality than many other teams in the league. Regardless, they're allowing more goals than their scoring chance against statistics would imply.

The underlying metrics have Philadelphia pegged as a team with a great power play and a middle-of-the-road penalty kill, yet the team finds itself near the bottom in both categories entering the season's second half. Are there any other teams facing the same problem, with solid shot and chance metrics but poor goal-based performance?

How unlucky have the Flyers been?

It doesn't take hardcore statistical analysis to understand the theory behind using shot and scoring chance metrics to judge the effectiveness of a team's penalty kill and power play. If a team is taking lots of shots and creating tons of scoring chances, they will probably score a lot of goals over the long-term. By the same token, if a penalty kill doesn't allow many shots or scoring chances, they'll probably allow less goals than a team whose penalty kill bleeds shots and chances against.

But there are always exceptions, and so far this year, the Flyers have been one of them. What becomes obvious after a closer look at the numbers, however, is that Philadelphia has actually seen the largest discrepancy of any team between their special teams shot metrics and their goal-based efficiency.

Using a fairly unscientific method, I tried to account for the importance of Fenwick, Shots on Goal, and both regular and high-danger scoring chances in trying to evaluate where a team's power play and penalty "should" rank in relation to the rest of the league.

To do this, I ranked every team in the NHL in each of the four categories, and then calculated their average finish across all four. This lets us note the importance of each aspect of special teams - shot generation/prevention and scoring chance generation/prevention - while filtering out the effect of save percentage and shooting percentage, both highly variable results. Using that average, I was able to create a rough list of the league's power play and penalty kills, ranked in order by the strength of their underlying metrics.

It turns out that no team has a larger negative gap between their "expected" overall special teams ranks and their actual position than the Philadelphia Flyers.

Team Current PP Ranking Expected PP Ranking PP Differential Current PK Ranking Expected PK Ranking PK Differential Total Differential Philadelphia 28th 3rd -25 25th 8th -17 -42 Toronto 15th 1st -14 14th 1st -13 -27 Arizona 19th 13th -6 23rd 4th -19 -25 Nashville 9th 21st +12 29th 3rd -26 -14 Detroit 23rd 13th -10 18th 15th -3 -13 Calgary 30th 24th -6 30th 23rd -7 -13 Vancouver 24th 15th -9 20th 19th -1 -10 Carolina 26th 18th -8 19th 17th -2 -10 Columbus 17th 6th -11 16th 20th +4 -7 Islanders 21st 10th -11 2nd 6th +4 -7 Florida 25th 22nd -3 9th 7th -2 -5 Boston 1st 4th +3 8th 1st -7 -4 Los Angeles 11th 6th -5 11th 14th +3 -2 Montreal 18th 17th -1 6th 5th -1 -2 Edmonton 27th 20th -7 15th 22nd +7 0 Buffalo 8th 9th +1 27th 26th -1 0 Rangers 12th 19th +7 17th 10th -7 0 Winnipeg 29th 27th -2 26th 29th +3 +1 Minnesota 22nd 16th -6 21st 30th +9 +3 Washington 2nd 2nd 0 10th 15th +5 +5 Ottawa 20th 25th +5 28th 28th 0 +5 Dallas 4th 11th +7 13th 12th -1 +6 Tampa Bay 16th 26th +10 22nd 21st -1 +9 San Jose 7th 6th -1 12th 24th +12 +11 Anaheim 10th 12th +2 1st 11th +10 +12 Pittsburgh 13th 5th -8 5th 26th +21 +13 Colorado 5th 23rd +18 24th 25th +1 +19 New Jersey 14th 30th +16 7th 13th +6 +22 Chicago 3rd 28th +25 10th 15th +5 +30 St. Louis 6th 29th +23 3rd 17th +14 +37

(All statistics accurate as of 1/11)

Most teams fall close to their expected rankings. In fact, half the league is performing within ten spots of their underlying shot and scoring chance statistics when it comes to special teams. But there are exceptions, and the Flyers headline the list. Their power play has underperformed by 25 spots in the rankings, and their penalty kill by 17 spots, giving them a combined differential of negative-42, by far the worst in the NHL.

The Flyers are actually one of only four teams (alongside Toronto, the Islanders and Boston) to rank in the top ten in Expected Efficiency for both the power play and the penalty kill. This hints that the process behind their special teams is still relatively sound, and that both units should improve in the season's second half.

Conclusion

The Flyers' special teams have been one of the biggest disappointments for the team so far in 2015-16. For the first time in years, Philadelphia finds themselves near the bottom of the charts in both power play and penalty kill efficiency, and for a team that can be best described as "middle-of-the-road" at even strength, a weakness in special teams can be devastating.

But there are reasons for optimism. The Flyers' power play actually has stellar underlying indicators, as the team ranks near the top of the NHL in both shot and scoring chance generation on the PP. It's been a league-low 9.6% shooting percentage that has buried the power play in the first half, not their underlying performance. Even a slight bump in shooting percentage combined with continued above-average shot generation statistics should result in a climb up the goal-based efficiency rankings.

The penalty kill does have some issues, particularly in preventing scoring chances against, but they too are performing below their underlying statistics. The biggest issue facing the shorthanded units this season has been the uncharacteristically poor play of Steve Mason, who has posted a league-worst 78.95% save percentage while facing opponents' power plays.

The good news for the Flyers is that Mason's career save percentage while shorthanded is far better, coming in at 86.09%. Since Mason is still in his prime and has not faced a deluge of high-danger chances this season relative to the league at large, it's most likely that his performance on the penalty kill will fall closer to his career averages through the rest of the season. If Mason improves and the current shot prevention percentages hold, Philadelphia should at least ice a decent penalty kill in the season's second half.

The power play and penalty kill may have underachieved in the first 40 games of the year. But there's every reason to believe they will bounce back in the season's final three months.