He was converted to defensive end as a sophomore, starting eight of 12 games and tying a career-highs with 37 tackles (10 for loss), two forced fumbles and a sack.

He tied a single game career high with seven tackles at Auburn to earn SEC Defensive Lineman of the Week honors.

He helped the Tigers win the Southeastern conference (SEC) Championship and finish 13–0 by defeating Virginia Tech in the Sugar Bowl, in which he made three tackles.

The next year, he was considered one of the dominant players in the league, earning All-Pro honors, after registering 40 tackles (29 solo) and 6 sacks.

He missed four games with a high ankle sprain and also suffered a groin injury that put him on the injured reserve list.

During his rehabilitation process, Ratliff relationship with the team's medical staff and even with owner Jerry Jones became tense.

The Cowboys still saw him as key player in the new 4–3 defense, even after assigning him to the Physically Unable to Perform list at the start of the year.

An already acrimonious release escalated after Ratliff's agent (Mark Slough) held a conference call on October 16, where he publicly stated that it was a serious pelvic injury that would likely take at least a year to heal.

[10] On October 23, the controversy heated up when Ratliff was cleared medically to work out for other NFL teams, only a week after being released.

[15] He missed five games due to injuries, but was still considered the best player on the defense, finishing with 6.5 sacks (second on the team) and 33 quarterback pressures.

Ratliff was suspended by the NFL for the first three weeks of the 2015 regular season for violating the league's Policy and Program for Substances of Abuse.