When Randy Carlyle was fired by the Toronto Maple Leafs on Monday, one of the main reasons was the organization's recent push for more data-driven decisions.

And the data on Carlyle was damning.

It's extremely difficult to boil something as complicated as running a hockey team down to one number, but what was hard to miss when watching the Leafs was how little they had the puck and how badly they were outshot.

A mediocre team in this department under former coach Ron Wilson, they became almost unbelievably poor once Carlyle arrived. Over his nearly three years and 188 games, the Leafs were a 43.5 per cent possession team, one of the lowest numbers ever in that long a span.

Believe it or not, that is a very good spot for interim coach Peter Horachek to step into.

Measuring how a coach impacts play in the NHL isn't easy. They're often credited with good special teams, but what exactly makes a good coach at even strength varies depending on who you ask.

Recent history, however, shows us that a coach can have a huge influence when taking over a poor possession team.

Over the last seven seasons, the 10 biggest improvements in possession featured seven teams that changed coaches. In several cases, the coach on the way out was a former player or GM who was a demonstrably poor coach.

When the Phoenix Coyotes went into bankruptcy and Wayne Gretzky was forced out as coach, for example, his replacement was Dave Tippett, one of the top coaches in the game. That first season, 2009-10, the Coyotes possession skyrocketed up 6.5 per cent – from 45 to 51.5 per cent – the biggest year-to-year shift since the data has been available.

A great player, The Great One was a poor coach – and the numbers showed it.

Tippett was named coach of the year.

Other examples are similar. Joel Quenneville improved the Blackhawks possession by 5.7 per cent in 2008-09 over what Denis Savard managed. Michel Therrien improved the Habs' by about the same in 2012-13 in taking over for a clearly overwhelmed Randy Cunneyworth.

More recently, Jon Cooper replaced Guy Boucher and the Lightning improved by 5 per cent last season.

This year, they're up another 4 per cent again and one of the best teams in the league.

This isn't an exact science – not every firing pays off this way and some teams improve possession-wise because of an improved roster – but it's clear that a coaching change can be a significant boost.

In Horachek's case, even his first two games behind the bench have been instructive. He has tried to implement a much different breakout than Carlyle's, for example, with his centremen back deep in the zone to help, and the Leafs have been outshooting their opponents.

"We're bumping pucks to the middle more than rimming it around the wall, and it's letting us get out of our zone cleaner," Leafs centre Tyler Bozak explained to TSN in the intermission of a 5-2 win over Columbus on Friday. "We're spending a lot more time in the offensive zone so that keeps them playing defence."

That's a very simple strategic shift, but it's only one example of something a new coach can introduce that shows up in the data.

In this small sample size, the Leafs have had 51 per cent of the shot attempts and 59 per cent of the scoring chances at even strength, which are both dramatic improvements.

Horachek's methods will now be in for a very tough test this week, as Toronto will face four of the best teams the league in the next six nights.





The NHL’s most improved possession teams (2007-2015)

Teams Season Possession change Year 1 coach Year 2 coach 1 NYI 2014-15 6.7 Capuano Capuano 2 PHX 2009-10 6.5 Gretzky Tippett 3 TB 2010-11 6.1 Tocchet Boucher 4 LA 2008-09 5.8 Crawford Murray 5 CHI 2008-09 5.7 Savard Quenneville 6 MTL 2012-13 5.6 Cunneyworth Therrien 7 MTL 2010-11 5.1 Martin Martin 8 MIN 2012-13 5.0 Yeo Yeo 9 TB 2013-14 5.0 Boucher Cooper 10 ATL 2008-09 4.5 Waddell Anderson