Tim Rattay has averaged the fewest passing yards per attempt by a 49ers quarterback in a season, with -4.0 yards in his rookie season in 2000.

fewest++ yards+per+attempt+by+a+qb+vs+niners+this+season+10+++ attempts
Interpreted as:
fewest++ passing yards+per+attempt+by+a+qb+vs+niners+this+season+10+++ passing attempts

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