To offer up some historical context, New York Jets QB Joe Namath was the first quarterback to throw for 4,000 yards during one season, back in 1967.
The 10 QBs on pace for 4,000 yards this season are:
Tom Brady (2,686 yards in 9 games) on pace for 4,775
Brett Favre (2,406 yards in 8 games) on pace for 4,812
Tony Romo (2,308 yards in 8 games) on pace for 4,616
Carson Palmer (2,193 yards in 8 games) on pace for 4,386
Drew Brees (2,175 yards in 8 games) on pace for 4,350
Derek Anderson (2,108 yards in 8 games) on pace for 4,216
Peyton Manning (2,058 yards in 8 games) on pace for 4,116
Donovan McNabb (2,044 yards in 8 games) on pace for 4,088
Matt Hasselbeck (2,023 yards in 8 games) on pace for 4,046
Jon Kitna (2000 yards in 8 games) on pace for 4,000