Everybody around here hates Rob Johnson and probably rightly so (unless his walk rate is sustainable. Every passed ball causes another M's fan's head to explode. That said, I started thinking about Mariners catchers and how Rob Johnson would rank amongst them. Besides Kenji, Dan Wilson and Dave Valle I couldn't come up with any Mariners catchers worth anything. I went to Rally's historic WAR database and hunted down all the players who ever played catcher for the Mariners (baseball reference). Then I made myself a little spreadsheet where I have broken down each player by the amount of WAR produced over their whole career as well the amount of WAR accumulated while they were a Mariner. I also included WAR/season as well as the best (Peak) and worst (Valley) seasons they had as Mariners. Rally's database only goes up until 2009 so I updated active players by adding their contributions from this season using Fangraphs.
(Click on table to enlarge)
What we see from this is that there really have only been a few M's catchers worth anything and none of them have ever been an elite player. One thing that goes into this is that the Mariners haven't been around that long and there haven't been that many starting catchers. From this list, catchers have contributed 29.6 WAR and over 34 seasons this works out to 0.87 WAR per year which is pretty bad but not too surprising since the Mariners historically have been a below average team and before Dave Valle came around had basically nothing at catcher. Also from this chart we see that the franchise has has only 3 catchers who have really been "good" catchers. Dan Wilson, Kenji Johjima and Dave Valle contribute exactly 29.6 WAR which happens to be exactly the same number as the overall M's total (I double checked this and this is a weird coincidence). Without those three we would see that overall the contribution from all other catchers has been at replacement level.
We also see Wilson has the highest overall total but Kenji has higher per year numbers. I think we can make an argument that one of these two is the best mariners catcher however its difficult to pick one over the other. They both had good peak years where Dan had 2 years ('96-'97) with WAR totals of 3.3 and Kenji had one year with a WAR total of 3.4. Dan always had a great defensive reputation and his success over his career was tied to above average defense. Kenji did not have this reputation while he was here but still scored very highly (+14 runs) during his peak year which is very surprising to me. On the other end of the spectrum Scott Bradley (others were also really bad) somehow stuck around for half a decade with horrible production both with the glove and the bat. Scott Bradley literally had 200 good PA in 1986 and rode on the coat tails of this for the rest of his career.
I thought this was cool. I might do this for other positions if people are interested. I'll end with a bold statement.
Best M's Catcher of All Time: Dan Wilson
Worst M's Catcher of All Time: Scott Bradley