Nothing brings me out of a writing slump like someone posting something about win rates.

The post in question today was by Chris Wheatley from Football London:

Arsenal’s best right-back as Cedric, Bellerin and Chambers compete
Mikel Arteta has a new mainstay in defence after statistics showed that the Gunners win more games with Cedric Soares at right-back

The main thrust of the article was about how Cedric is the better choice at right back because when he plays there Arsenal win more often.

This is certainly a true fact but looking at things just this way is incredibly misleading. This isn't to dismiss the idea that Cedric is a better choice for Arsenal, and I have already compared them previously so I won't wade into that argument again.

Comparing Cedric vs Hector
After last weekends match against Leicester City, one of the talking points of“Arsenal Twitter” was should Cedric Soares be starting over Hector Bellerin,especially when Arsenal play with Nicolas Pepe? I guess the first place to start is with my priors, which I am writing beforereally looking in…

What makes this measure so misleading is that it doesn't account for the strength of opponents at all, nor that draws also get you points and can be good results as well (or even a loss that still has the team advance like the last match against Olympiacos).

To illustrate the differences between the level of teams that each has played against, I used the closing betting odds and coverted those into the implied odds of Arsenal winning. This makes things look quite a bit closer.

My win% numbers are slightly different and I am not sure why, I have given each player credit for playing any match at RB or RWB for Arsenal this season.

You can see that Arsenal do win more matches when Cedric Starts but they are also expected to win more often in the games that he has started. The performance for Bellerin also matches much closer to the expected winning (but slightly below expected).

To put things in a bit of perspective, in the matches Cedric has played Arsenal are epected to take 2.1 points per match, it is 1.9 for matches where Ainsley Maitland-Niles played Arsenal, 1.8 for the matches played by Callum Chambers and 1.6 for the matches that Bellerin played in.

There are certainly reasons to point to if you want to say Cedric is the better option but using win rate is a poor choice.