Is the Attack or Defence side assignment biased in Rainbow Six Siege?

Sadnan Nafis
By Sadnan Nafis
5 Min Read
Image: Ubisoft

In Operation Phantom Sight, Rainbow Six Siege introduced the 3-round rotations in Ranked mode. According to the devs, the division of starting Attack or Defence first was completely random.

However, a year ago there was an uproar in the Siege community, complaining about their matchmaking being clearly biased. Even Siege Pro player Pengu tweeted out stating “85-90% of his games are on Attack”.

Although in Y4S3.2 patch update, Ubisoft reported that they had fixed the Attacker lopsided matchmaking bug.

  • FIXED – Fixed an issue with Attacker side logic bias during lobby creation. Attacker and Defender side assignment is now completely random.

Afterward, there were still complaints about this unfair matchmaking system, and popular streamer Annemunition also noticed this throughout her matches.

Bl0n, R6 Analyst developer, went deep into his matchmaking data and shared all his findings on Reddit today. He collected a dataset of over 21500 Ranked matches, all played in the past 45 days to explore the issue of how Siege divides up who starts on Attack and Defence.

However, Bl0n had to look at individual player’s data, so he ended up with 282 players who had played 12871 number of Ranked matches. Here’s what his findings had to say:

Data Analysis

(Terms: ‘Orange’ for defence-first, and ‘Blue’ for attack-first)

An analysis of 12871 Ranked matches across 282 players from all over the world, show quite definitively that there is some lopsided bias in the division of Orange and Blue teams. A statistical analysis (binomial distribution, p-value ≤ 0.05) shows that for 43.6% of players, the division is not a purely random 50/50 chance. And a subset of players (<15%) are “stuck” with receiving either Orange (defence-first) or Blue (attack-first) on nearly all (>75%) of their matches.

Of the 282 players, there were 123 for whom the matchmaking appears to be statistically significantly different from a random 50/50 chance of receiving Orange or Blue. This means 43.6% of players are getting something other than a 50/50 random chance for team colour during matchmaking.

For 15% of the players in the dataset, this biased matchmaking is very extreme, with at least 75% of their matches starting on the same side. Some explicit examples are;

  • A player with 153 matches tracked, with 138 Orange and 15 Blue.
    • That’s a 90% chance of starting Defence first!
  • A player with 121 matches tracked, with 107 Orange and 14 Blue.
    • 88% chance of starting Defence first.
  • A player with 241 matches tracked, with 50 Orange and 191 Blue.
    • 79% chance of starting Attack first.

Possible Causes

Bl0n then explored the reasons for these unusual results. Last year, the rumors flying around were that it had to do with your Ping in-game. Alternate explanations had to do with how many you were stacking with when entering matchmaking.

He then contacted some of the other players that were getting extremely significantly biased matchmaking (>75% going one way or the other), to ask their usual ping and matchmaking.

Only three players responded-

  • They all get Orange in almost all matches.
  • They all have a ping of 9ms.

However, one says he almost always plays solo-queue, whilst the other two mainly queue in 4- or 5-stacks. They get Orange in ±80% of their Ranked matches. One of them has played 168 matches last month, with 134 of them on the Orange team.

Bl0n was also able to determine that at least three of the players that are assigned Blue team a statistically significant amount of times, are located in countries that are commonly associated with having a higher-than-average ping.

Unfortunately, none of these results have concrete evidence to conclude something. But according to Bl0n, there is definitely still something funky going on with how matchmaking works. But now it’s up to Ubisoft now to verify these findings and acknowledge if this issue still persists in the game.

Sadnan Nafis is a Senior Esports Writer at GameRiv. Sadnan has a love-hate relationship with Rainbow Six Siege. He loves to keep himself updated with new tech videos and is always ready to help others.