Published: Apr 13, 2012 6:23 PM EDT
Updated: Apr 14, 2012 6:32 AM EDT

FAYETTEVILLE, Ark. (AP) - Former Arkansas coach Bobby Petrino said Friday that he won't appeal his firing and seek any of the $18 million buyout that was part of his contract while the university put his ex-mistress on paid leave following the revelation of their affair.

Petrino's agent, Russ Campbell, sent an email to Arkansas athletic director Jeff Long late Thursday saying Petrino has accepted "responsibility for the events that led to the university's decision to terminate his contract."

"Coach Petrino and his family wish nothing but the best for both the Razorback football program and University of Arkansas," Campbell wrote.

Petrino was fired Tuesday for failing to disclose his relationship with football staffer Jessica Dorrell and withholding other information from Long, including that he had once given her $20,000 for reasons that have not been disclosed. Petrino hired Dorrell four days before the April 1 motorcycle accident with her that led to his downfall.

Petrino had the option to appeal the firing as part of the seven-year contract he agreed to in December, 2010. The contract was for more than $3.5 million annually and carried an $18 million mutual buyout clause in 2011 and 2012. The amount dropped over the life of the contract, falling to as little as approximately $3.9 million in 2017.

Long said that Petrino was fired for cause, meaning the coach was not owed any of the buyout.

While Petrino's employment at Arkansas is over, Dorrell's future at the school is still undecided.

University spokesman Steve Voorhies said the 25-year-old football department employee has been placed on paid leave. Voorhies wouldn't issues any more details because the situation is a personnel matter.

Dorrell, a former Arkansas volleyball player, was a Razorback Foundation fundraiser before she was hired as the football team's student-athlete development coordinator by Petrino on March 28. Her salary is $55,735.

Long said the two had been in a relationship for a "significant" amount of time and phone records show they exchanged more than 4,300 text messages and nearly 300 phone calls over the past seven months.

In a March 20 letter Long sent to Dorrell offering her the job, he wrote that "you should be aware that you will be held accountable for and must abide by University of Arkansas, Southeastern Conference and NCAA rules and regulations."

The school, he added, "expects integrity" and Dorrell was asked to comply with "conflict of interest policies" among other things. The letter amounts to an "understanding" that there are "no agreements, whether written or oral, regarding your employment other than those contained in this letter." The letter was signed by Dorrell.

A person familiar with the situation has told the AP that Dorrell had "at one time" been engaged to another athletic department staffer, assistant strength and conditioning coach Josh Morgan. Voorhies said Morgan, who has held that title since 2009, is still employed by Arkansas.