Hall of Fame quarterback Warren Moon didn't begin his professional football career in the NFL. Despite ending his college career by leading the University Washington to a upset over the heavily favorite University of Michigan in the Rose Bowl, he was not drafted in the 1978 NFL Draft.

Moon got the chance to play in the Canadian Football League and became a star. After leading the Edmonton Eskimos to five consecutive championships and winning two league championships, Moon jumped to the NFL as the Houston Oilers starting quarterback.

The rest, as they say, is history -- huge passing numbers history. If you combined his NFL and CFL stats, his numbers are nearly unmatched in professional football annals: 5,357 completions in 9,205 attempts for 70,553 yards and 435 touchdowns. Even with just his NFL numbers, Moon's career was exceptional: 3,988 completions for 49,325 yards, 291 touchdown passes, 1,736 yards rushing, and 22 rushing touchdowns.

Warren Moon was elected to the Pro Football Hall of Fame in 2006.

What was Warren Moon's greatest career achievement?