I need to block my opponent's potential diagonal win. They currently have X at positions (0,2) and (1,1), which forms a diagonal line that would complete at (2,0). By placing my O at (2,0), I prevent this diagonal win.

Additionally, this move is strategically strong for me because:
1. It creates a potential vertical winning line with my existing O at (0,0)
2. It controls a corner position, which gives me more options for future moves
3. It forces my opponent to play defensively rather than offensively

If my opponent doesn't block at (1,0), I can create a winning threat on the left vertical column in my next move.