This perplexed Mariner fan does not see Seattle as a likely destination for Giancarlo Stanton.
The Mariners have some money to spend with only $92.6 million committed to 2018 after a 2017 payroll of about $155 million:
https://docs.google.com/spreadsheets/d/1FPmVBnzTPHvWfnpemP2Dt_CRyg7Mf12wW62BpgNjxIY/edit#gid=0
However, the core of Robinson Cano, Nelson Cruz, Kyle Seager, Jean Segura, Mike Zunino, James Paxton and Felix Hernandez is not particularly young as they enter their age 35, 37, 30, 28, 27, 29 and 32 seasons.
Seattle lacks an ace as an aging Hernandez has lost that status and injuries have slowed James Paxton's ascent to that status.
Over the past two seasons the Mariner hitters have ranked second in the American League with a wRC+ of 105:
http://www.fangraphs.com/leaders.aspx?pos=all&stats=bat&lg=al&qual=0&type=8&season=2017&month=0&season1=2016&ind=0&team=0,ts&rost=0&age=0&filter=&players=0&sort=16,d
Meanwhile, Seattle pitchers ranked 12th in the league in fWAR this year:
http://www.talksox.com/forum/threads/18478-Stanton-or-Votto/page11
... and 11th in ERA+ at 96:
https://www.baseball-reference.com/leagues/AL/2017-standard-pitching.shtml
According to MLB Prospect Watch, Seattle has only one prospect in the Top 100, outfielder Kyle Lewis at No. 41:
http://m.mlb.com/prospects/2017?list=prospects
The Mariners are more likely to pursue Shohei Ohtani than Giancarlo Stanton.