Something like this should work;
SELECT
SUBSTRING_INDEX(
LEFT(description,
GREATEST(LOCATE(' yards (', description),
LOCATE(' yard (', description))-1), ' ', -1)
FROM nflPxP
While this query works for a row that is fetched by some other search criteria, it's not indexable, so you may want to just add a separate column to store the data if searching the data is required.