Can we predict the winner of the 2015 NRL grand final?

The Sydney Roosters head into the National Rugby League (NRL) finals close to unbackable favourites to win the October grand final. But my detailed analysis of the past 12 premiers shows that your money may be better kept in your pocket for now.

If Roosters coach Trent Robinson’s men are to make good on expectation, they will have to overcome serious shortfalls in statistical categories that history tells us are vital.

I’ve looked at all eight finals teams across 27 key performance indicators. These include the average age of the team, the average number of NRL games, the number of state and international players and even the experience of the coach.

The Roosters are above average in only five of these, despite what their A$2.75 betting odds for the title may have you believing.

Compare this to the dark horse of the competition, Melbourne Storm, which ranks above average in 18 of my 27 statistical categories.

These are stats based on 12 years of history – unlike other stats such as possession percentages, missed tackles or metres gained, all of which can fluctuate wildly from one week to the next. While those performance keys can be overcome with a concerted team effort on the day, it takes much more to compensate for shortfalls in the area of experience.

One glaring statistic relates to what we commonly refer to nowadays as the spine of the team – the key directional and playmaking positions of hooker, halfback, five-eighth and fullback.

Over the past 12 seasons, premiership-winning teams have an average of 513 games of NRL experience between the players in these pivotal roles.

The Roosters spine, consisting of Jake Friend, Jackson Hastings, James Maloney and Roger Tuivasa-Scheck, has 412 games worth of experience. In comparison, the spine of the Storm has 660 games in the NRL, while the Broncos and Sharks also hover around the 600-game mark.

Of course, this could all change if injured Roosters halfMitchell Pearce comes back into calculations later in the finals, but for this week at least, it’s certainly food for thought.

Age of players

Much debate exists over the perfect composition of a squad, based on age. How many old heads is too many? And do fresh young legs need a dollop of maturity to help steer them in the right direction?

Analysis of premiership squads from 2003 onwards shows the ideal number of players aged 18 to 21 is five, the bulk of the squad (average of 11 players) should be 22 to 25, you need seven players aged 26 to 29 and two more aged 30 to 33.

Only Manly in 2008 and the Rabbitohs in 2014 won a premiership with a player older than 34 in their squad, and they were some pretty exceptional blokes in Steve Menzies and Lote Tuqiri.

In 2015 the club that bests fits the age-distribution model is the Bulldogs. The Dogs also come out favourably if you do a more simplistic split and say that grand final-winning teams average 10 players aged 25 and younger and seven players aged 26 and over.

In this regard, the Storm and Rabbitohs also come up looking good, while the Sharks are a definite worry. Sharks captain Paul Gallen and his charges boast a squad with six players over the age of 30 and an average age of 27 years and 307 days, the oldest of any team left in the finals.

Across the past dozen years the ideal average age is 25 years and 107 days.

An interesting one is the Cowboys, who despite a swift, attacking reputation have an average age of 26 years and 288 days and may have missed their premiership window.

Should the North Queenslanders raise the trophy, they will be the oldest team to do so in more than a decade.

Experience

Age is not everything of course and there is a difference between the date on a birth certificate and the number of NRL games played.

The late, great Ray Stehr had played 10 seasons of first grade when he was 26, the same point in life at which Manly’s Brenton Lawrence made his debut.

My analysis measured 12 categories concerning experience, with a key result being that the average number of NRL games for premiership teams from 2003 to 2014 was 86.5 per player.

Again there are a few red flags here for the Roosters, who have an average experience of just 75 games per player and no player with more than 200 games experience.

I wouldn’t say experience is everything, however, with one finding being that premiership squads over the past 12 years have fielded an average of six players with fewer than 25 games under their belt.

Having two or three players with more than 200 games experience seems to be a trigger for success, although the Storm of 2012 were an exception with five players over that mark.

Not surprisingly, quality of experience has a big bearing. Winning teams between 2003 to 2014 averaged four State of Origin players in their ranks and 7.5 internationals in total.

The only team that fulfils both these criteria in 2015 is Melbourne.

The all-important spine

As mentioned earlier, the players with numbers 9, 7, 6 and 1 on the backs of their jerseys have been shown to be highly influential in premiership outcomes.

The average number of games played by a hooker at the time of winning a premiership in the last 12 years was 123, the average for a premiership halfback was 134, the average for a five-eighth was 104 and the average for fullback was 153.

No team fits this distribution perfectly, with the closest being the Broncos quartet of Andrew McCullough (172 games), Ben Hunt (138), Anthony Milford (66) and Darius Boyd (220).

Melbourne has the most total games experience in their spine, but this is heavily influenced by two players in Cameron Smith (304) and Cooper Cronk (269). Cameron Munster and Blake Green are considerably less experienced.

Influence of the coach

While skewed by the Broncos' Wayne Bennett’s longevity as coach, the average number of seasons a coach has needed to be with a club before winning a premiership in recent times is six.

The average age of a premiership coach over the past 12 years has been 50. That might indicate bad news for young guns Trent Robinson, Michael Maguire and Paul Green if two of them hadn’t already won it!

Melbourne again comes out looking good when I cross-reference a broad range of coaching categories, mainly by the stability that coach Craig Bellamy has achieved in 13 successive years at the one club.

Limitations in the analysis

In any study like this, there are going to be anomalies that distort statistics week-to-week.

To prepare this report, I took into account all players who took the field in Round 25, which means the likes of Mitchell Pearce and Rabbitohs’ spearhead Greg Inglis do not feature.

But we know teams named for this weekend could still change – someone could be suspended afterwards, or further players injured before the grand final. Some clubs also name larger squads than others.

In order to achieve precise statistics based on 17 players per team, I had to nominate a recent round for which all data was available.

By taking into account 27 categories, the objective is to create a broad picture that is not be distorted by the absence of a handful of players.

Based on this analysis my money would be on the Storm who come up trumps in more categories than any other team.

Regardless, we know that history exists to be bettered, and by the end of these finals we will have new numbers to define the competition’s leading performers.

It doesn’t hurt to speculate though, does it?

The University of Queensland is the official university partner of the Brisbane Broncos. Vincent Kelly is currently co-supervising several undergraduate and postgraduate students at the Brisbane Broncos.