Prospect Juan Then: Seattle Mariners Instructional League

SEATTLE, WASHINGTON - JULY 19: Juan Then, a Mariners prospect, pitches. (Photo by Abbie Parr/Getty Images)
SEATTLE, WASHINGTON - JULY 19: Juan Then, a Mariners prospect, pitches. (Photo by Abbie Parr/Getty Images) /
Juan Then of the Seattle Mariners pitches.
SEATTLE, WASHINGTON – JULY 19: Juan Then of the Seattle Mariners pitches in a summer workout intrasquad game. (Photo by Abbie Parr/Getty Images) /

Seattle Mariners prospect Juan Then pitched well in his four outings during the Instructional League

Juan Then is the 14th ranked prospect in the Seattle Mariners organization and is just 20-years-old. Then reached Single-A in 2019 and participated in summer workouts at T-Mobile Park prior to the 2020 regular season. The right-handed starting pitcher threw in four games in Arizona, according to Mariners PR.

In his four outings before the instructional league was shut down, he pitched 6.1 innings and only allowed one run. Then also limited opposing batters to a .261 average. He faced 23 batters during the short instructional league. The prospect walked three batters and stuck out six. Based on my approximations with limited published statistics, Then averaged a 96mph fastball.

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The young pitcher has an interesting history with the Seattle Mariners because he was first signed by Seattle in 2016. He would be traded to the New York Yankees in 2017 after the regular season in exchange for Nick Rumbelow. Seattle General manager Jerry Dipoto would bring back Juan Then at the 2019 trade deadline when Seattle traded away Edwin Encarnacion to the Yankees.

According to, he consistently sits in the 92-94mph range but his Instructional League numbers say otherwise. As a young pitcher, he still has room to grow and his fastball could increase a couple of ticks more. His fastball also has good life making it tough on hitters. Then also mixes in a hard slider and a changeup which has potential.

Juan Then is currently the 14th ranked prospect for good reason and hopes to join the big league team in 2022. There is not a lot to take away from the Instructional League due to the small sample size, but the one thing we can learn is that Then’s fastball velocity was up. Then should continue to rise up the ranks of the Seattle Mariners prospect lists as more graduate over time.

Then is an exciting overlooked prospect in the organization and has the potential to break the MLB Top 100 prospects list in a couple of years so keep your eyes on him.

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