Will Zunino build off breakout 2017 campaign?

With Spring Training now just two weeks away, it's time for an in-depth look at the Mariners' roster. This is the first part of an Around the Horn series looking at each position on the team. We'll start today with the catchers.
The big question: Just how good can Mike Zunino be for a full season?
There's no doubt the 26-year-old is now entrenched as Seattle's primary backstop. After being rushed to the Majors at age 22 in 2013, Zunino quickly proved he could be a quality defensive catcher, work well with pitchers and provide some nice power. But making contact at the plate remained an issue, and he came into last season with a career .195/.262/.370 slash line and lingering questions of whether he'd ever figure it out.
But after getting off to a slow start again last season, Zunino went down to Triple-A Tacoma for several weeks to work on some serious swing changes and his approach at the plate. After returning to Seattle in late May, the 2012 first-round Draft pick put up some of the best numbers of any catcher in baseball with a .270/.349/.571 line with 25 homers and 62 RBIs in his final 100 games.
If Zunino can maintain that production over a full season, he'll not only be one of the Mariners' top players but also one of the most-productive catchers in baseball. He already was second among all big league catchers in slugging percentage at .509, third in homers with 25 and fourth in OPS at .840.
The starter: Zunino
Even with his slow start -- he was hitting .167 with no homers and two RBIs in 24 games when he was demoted May 5 -- Zunino ended the year with the second-highest Baseball-Reference WAR on the Mariners, trailing only Nelson Cruz at 3.3. That was the best WAR by a Mariners catcher since Dan Wilson's club-record 3.8 in 1997.

Zunino posted a huge June with 10 homers and 31 RBIs, and he also finished strong in August and September. He comes to camp full of confidence and the knowledge of what worked so well with his new approach.
He still has things to work on, including blocking balls and lowering his strikeout rate. But the Mariners know that they have a player capable of producing at an All-Star level who is still under club control through 2020 and earning a very reasonable $2,975,000.
Backing up: Mike Marjama and David Freitas
This figures to be one of the more interesting roster battles in camp as the two 28-year-old rookies compete for the spot held last year by veteran Carlos Ruiz.
Marjama, acquired from the Rays in an August trade, went 3-for-9 with his first-career home run in five games as a September callup. Freitas, claimed off waivers from the Braves in October, made his MLB debut late last season as well and was 4-for-17 with two doubles in six games for Atlanta.
Both have put up solid offensive numbers at Triple-A, and the competition likely will come down to who impresses most behind the plate this spring.

Depth: Tuffy Gosewisch, Joseph Odom, Joe DeCarlo
Gosewisch, who is the veteran among the non-roster invitees to camp, is a 34-year-old with 137 games of big league experience, including 11 last year with Seattle while Zunino was sent down. The former D-back has never hit much at the Major League level. He's spent 11 years in the Minors, knows the game well and is an excellent clubhouse presence.
Odom, 26, was acquired from the Braves in the Minor League phase of the Rule 5 Draft in December. He's regarded as a strong defensive catcher but played just 28 games in Atlanta's Minor League system last year -- primarily in Double-A -- after suffering a broken forearm in spring. DeCarlo was a second-round Draft pick as a prep third baseman in 2012 but converted to catcher last year at Advanced-A Modesto.
In the pipeline
After trading 2017 fifth-round Draft pick David Banuelos to the Twins in December, there are no catchers listed among the Mariners' Top 30 Prospects by MLB Pipeline, which is why they selected both Odom and 24-year-old Tyler Baker from the D-backs in the Minor League phase of the Rule 5 process.
DeCarlo is another 24-year-old who could emerge, considering he was a well-regarded third-base hitting prospect when he was drafted. The Mariners sent him to the Arizona Fall League to get more experience behind the plate at the end of last season and will give him his first Major League camp experience this spring.
By the numbers
Perhaps Zunino should come out swinging again this season. He hit .600 (24-for-40) when connecting with the first pitch of an at-bat last year, the top mark in the Majors. In those 24 hits, he racked up seven doubles, six home runs and 17 RBIs.