Mariners Top 20 Prospects: #1 RF Alex Jackson

August 10, 2015; Vancouver, BC, CAN; Alex Jackson (10) up to bat for the Everett AquaSox against the Vancouver Canadians at Nat Bailey Stadium. Mandatory Credit: Brian Helberg-SoDo Mojo
August 10, 2015; Vancouver, BC, CAN; Alex Jackson (10) up to bat for the Everett AquaSox against the Vancouver Canadians at Nat Bailey Stadium. Mandatory Credit: Brian Helberg-SoDo Mojo /

Alex Jackson had a down year in 2015, but he remains one of the best power hitting prospects in all of baseball.

Alex Jackson easily has the most upside of any prospect in the Seattle Mariners organization, and he is the clear choice to be SoDo Mojo’s top youngster on the M’s farm. The 20-year-old outfielder is the 94th best prospect in the game entering the 2016 season according to, and he is Seattle’s lone representative in’s top 100 list.

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The Mariners selected Jackson with the 6th overall pick in the 2014 draft out of Rancho Bernardo High School in San Diego, CA. Jackson is believed to possess elite power from the right side, and he has the potential to hit for average at the big league level. Many pundits projected a fast rise through the Mariners system for Jackson, but poor plate discipline and injuries have slowed his development.

Jackson began last season with the Mariners single-A affiliate in Clinton. He looked overmatched in the Midwest League, posting a .157 batting average with 0 home runs and 13 RBI across 28 games with the LumberKings. Jackson’s .240 on base percentage and .213 slugging percentage suggest he was not ready for the level of competition.

However, Jackson was reportedly attempting to play through a shoulder injury he suffered with the Mariners in spring training. The M’s opted to shut him down once they caught wind of the ailment to prevent further damage physically and mentally. Jackson was idle for just over a month before being assigned to the Everett AquaSox of the Northwest League.

Jackson fared much better with the AquaSox this past summer. The young slugger registered a .239/.365/.466 slash line through 197 plate appearances. Jackson clubbed 11 doubles, 8 home runs, 25 RBI and swiped 2 bases in 48 games. Those numbers still leave something to be desired, but it took a mature attitude to recover from his horrid start in Clinton.

It is clear that Jackson did not play to his potential offensively last season. However, the former high school catcher looked significantly more comfortable as an outfielder in 2015. Jackson posted a .964 fielding percentage through 603 innings. His arm is incredibly strong, and he tallied 9 outfield assists during his time with the AquaSox. Right field appears to be his best position, but he has shown the ability to defend both corner spots.

The Mariners remain high on Jackson, and rightfully so. He played well in 2014, hitting .280 with 2 home runs and 16 RBI across 24 games in the Arizona Rookie League. Jackson also made a memorable impression during his first spring training with the Mariners in 2015, connecting on a home run during a game last March against the Texas Rangers.

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I happened to be in attendance during a game between the Everett AquaSox and the Vancouver Canadians at Nat Bailey Stadium in Vancouver, BC last summer. Jackson played right field and hit third for the AquaSox. Jackson destroyed a fastball in the top of the first inning, launching a 2-run shot that landed at least 50 feet beyond the left field wall. He finished 1 for 3 with a home run and a walk.

Jackson has an elite combination of size and skill. He stand tall at 6’2, and has a muscular 215 pound build. Jackson hits and throws from the right side. Scouts rave about his quick, powerful stroke at the plate, but he has the potential to be much more than just a power hitter. Jackson’s game is still developing, and it should be fun to watch him progress during the next couple of years.

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The 2016 season could be a turing point for Alex Jackson and his development. The Mariners are expected to take a patient approach with Jackson, and start him off once again with the Clinton LumberKings. Ideally, Jackson will dominate the Midwest League in his second go around and earn a mid-season promotion to the Bakersfield Blaze. Will that happen? Who knows. But he has the tools to be a thumper in the heart of the Mariners lineup one day.