A disk drive is disclosed comprising a disk having a plurality of data tracks, wherein each data track comprises a plurality of data sectors. A head is actuated radially over the disk in order to read one of the data sectors from a target data track on the disk. The data sector is stored in a buffer and decoded with an error correction code (ECC) decoder. When the decode fails, an erasure window is adjusted based on a number of non-read data sectors recorded in the target data track, wherein the erasure window comprises a length spanning at least one ECC symbol in the data sector. The data sector is read from the buffer and decoded with the ECC decoder using the erasure window.