The Mariners under Jerry Dipoto have paid significant lip service to their preference to make the roster "more athletic." They've since backed up that notion by trading Brad Miller for a package including Boog Powell, a fringe prospect that Dipoto seems higher on than most, primarily due to his on base and defensive abilities, exactly what he's stated he is looking for. But the need for outfielders, while real, is far from the only concern.
The Mariners roster for 2016 is a delicate, fragile beast. Due to the extremely misshapen state of things in Jack Zduriencik's wake there are obvious holes, and a minor league system that seems incapable of filling any in a particularly competent manner. However, this is not a franchise devoid of star level talent. With Felix Hernandez, Nelson Cruz, Kyle Seager and Robinson Cano the Mariners have the elite level talent to compete, provided the team surrounds them with competency. Enter the catcher position.
While Mike Zunino appears to have all the talent in the world to thrive on both sides of the plate in the major leagues his offensive production in 2015 was historically bad. Zunino should start the season in Tacoma, and while I don't propose the team give up on the idea of him as a major league starter, they certainly should not plan on it as anything approaching a realistic scenario.
The greatest Mariner teams ever were prime examples of the ability to leverage 3-4 stars by surrounding them with a complete, well organized 25 man roster, where every player was capable of providing to average to slightly above average major league play. It's time to return to that model, I think Dipoto wants to, and there's no spot on the roster more clearly a hole from which even the light itself cannot escape than the catcher position.
Chris Iannetta spent 2013 & 2014 as an underrated part of good Angel teams, sneakily posting a wRC+ of 112 and 126, respectively. Coupled with research that indicates his defense as among the best in the game and that version of Chris Iannetta would add as much as 2.5-3.5 wins over what's currently in house.
Of course, it's never that simple. Iannetta's offense collapsed in 2015, as he hit .188 and posted a wRC+ of a measly 80. It's always fun when trying to talk yourself into a potential buy low candidate to point at the recent failure and yell "OUTLIIIIIIIIIIIIIIERRRRRRRRRRRRRRRR" but then, that's not entirely how this works. Iannetta will be 33 in 2016, and the downslope of his career very possibly may be here. While I doubt he posts a wRC+ of 80 again next year, the halcyon days of yesteryear may be gone for good.
BUT, and this is the biggest point, even 2015 Chris Iannetta would have been the Mariners best catcher by a huge margin. For example, Chris Iannetta's wRC+ in 2015 was thirty-three points higher than Mike Zunino's. Again, this is with Iannetta batting .188. If you blend the average of Iannetta's last three years, weighting 2015 the heaviest as it's the most recent, I'm comfortable projecting him as a ~league average bat in 2016.
Fangraphs' crowdsourcing has Iannetta receiving a 2 year/12 million dollar. Even if they are low on the dollar amount I find it unlikely that any team is going more than 2 years. The Mariners have other holes to fill, but with Matt Wieters' decision to accept Baltimore's Qualifying Offer further thinning an already scant pool of catchers the Mariners have to act quickly. There is no greater need with a more obvious fix, and one at a relatively low money cost, not to mention that it doesn't lose the team a 1st round draft pick.
The team is aware of this, and I'm sure they're working hard to make it happen. Sometimes the obvious move is the best one. With a bounceback season Iannetta's signing will also further my personal theory that Jerry Dipoto is assembling the Mariners into the Screw Mike Scioscia Omnibus, which we as a site fully endorse.
Sign Chris Iannetta, then get to work on the more complicated questions. Do it now.