A team's success or failure each season depends on a lot of factors – injuries, playing talent, team harmony, coaching, key decisions in key moments. But one factor that can be hard to quantify is the effect of a "tough" or "easy" draw.

A draw doesn't make or break a team's premiership chances, but it does arguably have an effect on where teams sit after 26 rounds. For example, last year's grand finalists the Bulldogs only just scraped into the finals after battling through one of the league's most difficult fixture lists, while the Panthers stunned the critics with a top-four finish – possibly with help from the kindest draw in 2014.

What makes a tough draw? In a 26-round head-to-head competition, including two byes, all 16 NRL teams play each other once plus a second game against nine other teams. That means some teams will take on strong opposition twice, while others will face weaker teams more often. Of course there are other factors that determine how difficult a draw may be – travel, time between games, the effect of the Origin period – but here we're only focusing on the quality of the opposition.

We've analysed the draws of all 16 clubs and ranked their opponents during the season to determine who endured the hardest draw in 2015 and who had it easiest.

The toughest draw? Perhaps unsurprisingly, it was the Manly Sea Eagles – a perennial top-eight club who missed the finals this season. Apart from injuries and off-field distractions the Sea Eagles also had to contend with 14 fixtures against top-eight teams, with two matches against each of the Broncos, Cowboys, Storm, Sharks and Bulldogs.

At the other end of the scale was the Canberra Raiders, who finished the season with one of the best attacking records in the competition. Of their top-eight opponents they only had to play the Roosters and Sharks twice, while they played a combined eight games against the four bottom-ranked teams on the final NRL ladder. It wasn't enough to take the Raiders into the finals, but was arguably a factor in why they finished 10th rather than in the battle for the wooden spoon as many predicted at the start of the campaign.

We've given each opponent a "toughness" score based on where they finished after the regular season – 16 for minor premiers the Roosters, 1 for wooden spooners the Knights – and totalled up the score for each club's fixture list to give each team's draw a toughness rating for 2015. Here's how we've ranked the draws in 2015, from hardest to easiest.

1. Sea Eagles – 221 points

2. Dragons – 214

3. Rabbitohs – 213

4. Storm – 211

5. Broncos – 207

6. Knights – 206

7. Panthers – 205

8. Warriors – 204

9. Eels – 203

10. Roosters – 202

11. Wests Tigers – 201

12. Sharks – 200

13. Bulldogs – 198

14. Titans – 196

=14. Cowboys – 196

16. Raiders – 187

Note that a tough draw doesn't mean a poor finish for a team – the Rabbitohs, Storm and Broncos all faced among the toughest draws in the competition according to our system but still finished well inside the top eight. Meanwhile the Raiders, Titans, Wests Tigers and Eels all finished on the "easier" half of the list but still missed the finals. In fact, those teams who face a tough draw and still make the finals could potentially be in a stronger position for the business end of the season, having already experienced more games against top opposition.

Of course, the rankings are also skewed a little by where each team finished. Teams that made the finals are obviously going to have one less "top-eight" team to play against during the regular season as they can't play against themselves. And opponents vary in quality during the year – a Broncos team playing without their Origin stars isn't the same as a Broncos team at full strength, for instance. The same goes for a Warriors side with or without Shaun Johnson. But as a simple guide, this could be a clue why some teams finished higher than expected this season, and others finished lower.

We'll be back to analyse the 2016 NRL Telstra Premiership draw the same way when it's announced later this year.