In two seasons at Coffeyville, Carpenter vastly improved and soared to a four-star recruit by Rivals.com and Scout.com. He started every game at left tackle for the Red Ravens and was earned All-Conference honors twice. Although he remained an Iowa State signee, he began visiting other schools "just […] to make sure I make a good decision". He made official visits to Texas Tech, Oklahoma, and Ole Miss, before eventually committing to the Alabama Crimson Tide.
At Alabama, Carpenter faced the difficult task to replace All-American left tackle Andre Smith. While analysts did not expect him to dominate as a run blocker like Smith, they saw him as "a rock in pass protection".
Carpenter had a good post-season performance and, according to Sports Illustrated, went "from a third-round choice to a player who could be a surprise pick late in round one". He was selected with the 25th overall pick in the 2011 NFL Draft by the Seattle Seahawks. Carpenter started 9 games in his rookie season before suffering a season ending ACL injury and being placed on the injured reserve.