Since the Mariners acquired him in a trade with the San Diego Padres ahead of the 2015 campaign, Smith has posted a .248 batting average and .336 on-base percentage with 28 home runs, 105 RBI and 116 runs scored across 273 games with the organization.
His 16 home runs last season marked the second-highest total of his career behind only his 2010 campaign with the Colorado Rockies. He also set a new career high with 63 RBI.
The Ole Miss product attributed his success to a better approach at the plate after making some minor adjustments, per Bob Condotta of the Seattle Times.
"Just make sure you are getting started early enough," Smith said in July. "Some basic hitting things that sometimes you need to get back to."
He's also been better suited for a platoon role in which he starts only against right-handed pitchers. He owns a .355 on-base percentage and .827 OPS against righties compared to his .282 OBP and .594 OPS against lefties in his career, according to Yahoo Sports.
Ultimately, the Mariners decided he was worth the $7 million investment. The team's offense ranked sixth in runs scored last season, and picking up Smith's option leaves one less void to fill as Seattle attempts to match or exceed that output in 2017.
How the outfield will shape up probably won't become clear until after spring training. Smith could end up splitting time with Guillermo Heredia at one of the corner spots, but the team may thrust him into a full-time role if a platoon partner doesn't emerge.