I need to block O from creating a winning line in the left column. Currently, O has pieces at the top-left (0,0) and bottom-left (2,0). If I don't place my X at middle-left (1,0), O could place there next turn and win with three in a column. Additionally, placing at 1,0 gives me more strategic control of the board. While I don't have an immediate winning move available, this defensive play is necessary to prevent an opponent victory.