Last year, the 49ers had 21 passing touchdowns---23rd in the league.
Last year, the 49ers had 148 first downs by passing---dead last in the league.
I would argue that to understand the above stats, we have to consider that:
Last year, the 49ers threw a total of 417 passes---dead last in the league.
Here are some stats with the number of attempts factored in.
Not all stats are directly affected by the number of passes thrown. Here are some that are not, at least in my estimation.
[ Edited by buck on Apr 4, 2014 at 5:29 PM ]