I need to block my opponent from completing a diagonal win. Looking at the board, my opponent "X" has pieces at the top-right (0,2) and center (1,1), creating a diagonal threat. If they get the bottom-left (2,0) position, they'll win with a diagonal line.

By placing my "O" at position (2,0), I not only block their winning diagonal but also start forming a potential vertical line in the left column. I already have an "O" at the top-left (0,0), so placing at (2,0) gives me two positions in that column. If I can later secure the middle-left (1,0) position, I'll win with a vertical line.

This is both a defensive and offensive move that prevents an immediate loss while setting up a potential win.