The Brisbane born-and-raised nose tackle should be guaranteed a signing bonus of more than $200,000, and offered a $2 million contract by the Seahawks as the 137th selection of the draft - $5 million less than he would have received as a late first-round pick.

It is believed a knee injury affected Williams's draft stock, making potential suitors cautious about selecting the 22-year-old Queenslander, who had been touted as a 25th overall selection.

Williams had knee surgery (knee scope) following his Alabama team's demolishing of Notre Dame in January's national championship game, and he was unable to run at the NFL Combine.

Williams told followers on Twitter this morning after the pick was announced that: "The Wait is Over. Feels great to be a apart of the Seattle Seahawks  #timetowork #BacktotheWest."

Yesterday, he acknowledged his falling draft position by tweeting: "Did not expect it to be given to me that easy. #minorsetbackmajorcomeback #noworries"

The pick makes Williams the second highest Australian picked in NFL history.

New South Welshmen Colin Scotts was picked at number 70 (round 3) by the Cardinals franchise in the 1987 draft.

Williams will be playing for a professional team that hasn't tasted championship success during its 36-year history and have had only one Super Bowl appearance.

But the Seahawks have developed into a force in the NFC West division following the signing of former USC national championship winning coach Pete Carroll and Wisconsin quarterback Russell Wilson.

They made the NFL playoffs last season and look set to feature again this year with the high-profile signing of wide receiver Sidney Rice.

Williams began is American football career at the Bayside Ravens after arriving at training as a teenage novice to watch one of his friends play quarterback.

For four years he played for the Ravens in the Gridiron Queensland competition before going to school at Arizona Western.

He was recruited by the Crimson Tide after being named the top junior college prospect in the nation by Sports Illustrated.

During the final two years of his college career, Williams won back to back national championships with the Alabama Crimson Tide having transferred to Tuscaloosa in 2011 from Arizona Western college.

The 191cm, 145kg goliath nicknamed "The Monstar", was a key part of the University of Alabama's pair of national championships.

While playing for Alabama his mohawk, tattoos and Australian accent drew the attention of major US media outlets such as the New York Times and ESPN in the lead-up to this year’s national championship game.

But in the lead-up to the draft Williams has kept a lower profile, with attention centred around the depth of quality offensive lineman in the draft and the lack of star quarterbacks.

In recent years a number of Australians have broken into the NFL by way of their kicking skills.

Along with Scotts Williams is a rarity as the only Australian position players to be drafted.