I need to place my O at position (2,1) for two important reasons:

1. Defensive priority: My opponent has X markers at (0,1), (1,1), and could win by placing at (2,1) to complete a vertical column. I must block this immediate threat.

2. Setting up for a win: By placing at (2,1), I'm also creating two potential winning paths for my next move:
   - If I can later place at (2,0), I could create a winning bottom row [O, O, X]
   - If I can later place at (1,0), I would have two Os in position for a diagonal win

While there's no immediate winning move available for me this turn, this blocking move prevents my opponent's win while maximizing my future winning opportunities.