I have to claim ignorance since I didn't follow baseball closely that year. But just looking at the stats their overall pitching/defense was the best in the AL in limiting runs allowed - http://www.fangraphs.com/leaders.aspx?pos=all&stats=pit&lg=al&qual=0&type=0&season=2001&month=0&season1=2001&ind=0&team=0,ts&rost=0&age=0&filter=&players=0&sort=15,a which was partly because of a great defense - http://www.fangraphs.com/leaders.aspx?pos=all&stats=fld&lg=al&qual=0&type=0&season=2001&month=0&season1=2001&ind=0&team=0,ts&rost=0&age=0&filter=&players=0
In all honesty I am just asking a question here: do you think their success at limiting runs was because of their excellent defense (based on the stats)? They also led the league in offense, scoring 927 runs in 162 games - http://www.fangraphs.com/leaders.aspx?pos=all&stats=bat&lg=al&qual=0&type=8&season=2001&month=0&season1=2001&ind=0&team=0,ts&rost=0&age=0&filter=&players=0&sort=5,d. It helped their pitching/defense that they played in a pitcher friendly ball park - http://www.fangraphs.com/guts.aspx?type=pf&season=2001&teamid=0
Based strictly on the stats, the Mariners were a very well balanced team. Surprisingly, they lost the AL Championship to the Yankees 4 games to 1 - https://en.wikipedia.org/wiki/2001_American_League_Championship_Series. PS: I thought that maybe the Mariners played in a weak division in 2001, but actually it appears that the AL West was stronger than the AL East in 2001 - http://mlb.mlb.com/mlb/standings/index.jsp?tcid=mm_mlb_standings#20011007