NFL Rank on all downs (1st down, 2nd down, 3rd down)
(of top 10 rated passers)
Foles 1 (1, 1, 8)
Manning 2 (3, 2, 4)
Brees 3 (9, 5, 3)
Rodgers 4 (7, 4, 10)
Rivers 5 (2, 8, 17)
Wilson 6 (6, 3, 14)
Romo 7 (4, 6, 34)
Stafford 8 (16, 10, 9)
Ryan 9 (12, 9, 18)
Bradford 10 (8, 23, 22)
The 1st down rating carries more weight than 3rd down because there are 34% more pass attempts on 1st down than 3rd down. (Because there are more than twice as many 1st down plays as 3rd down plays). 3rd downs make up only 21.3% of all plays league-wide, and only 19.6% of the Cowboys' plays on offense. That's the reason Romo can rank 34th on 3rd down, but still rank 7th overall.
Which is not to say it isn't a terrible ranking, btw.