FAYETTEVILLE, Ark. â€"  Bobby Petrino has improved every step of the way at Arkansas - not just his team's performance but his image.

The coach's revelation Thursday of an inappropriate relationship and his attempt to cover it up now threatens to derail all the progress Petrino has made in four seasons.

Arkansas is expected to return to spring practice Friday afternoon, led by a pair of Heisman Trophy hopefuls in quarterback Tyler Wilson and running back Knile Davis.

The team will do so without Petrino, who was put on administrative leave Thursday night after athletic director Jeff Long learned Petrino had failed to disclose he had been riding with a female employee half his age when his motorcycle skidded off the road over the weekend.

Petrino said he had been concerned about protecting his family and keeping an "inappropriate relationship from becoming public."

It was as stunning admission for a highly successful coach who prides himself on complete control and intense privacy in his personal life. Petrino will now await his fate while Long conducts a review.

Whether his uncertain status affects the Razorbacks remains to be seen.

"I will fully cooperate with the university throughout this process and my hope is to repair my relationships with my family, my athletic director, the Razorback Nation and remain the head coach of the Razorbacks," he said in a statement issued by the university.

Long announced the decision to put Petrino on leave at a late-night news conference, one that was reminiscent of when the former Atlanta Falcons coach was hired by the Razorbacks on Dec. 11, 2007. Long said he had no timeline in determining Petrino's future with the Razorbacks.

"I'm at the beginning of the review. I don't know what I'm going to find," Long said. "I am disappointed that coach Petrino did not share with me, when he had the opportunity to, the full extent of the accident and who was involved."

Petrino just completed his fourth season with the Razorbacks, who have developed into a national contender under his watch - improving their win total each season. He's 34-17 in four seasons at the school, 21-5 over the last two, and the Hogs finished last season ranked No. 5 after losing only to national champion Alabama and runner-up LSU.

He came to Fayetteville after a 13-game stint with the Atlanta Falcons in 2007 season. He endured plenty of criticism on his way out of Atlanta, from fans and former players alike, for leaving at midseason.

Before that he was at Louisville, guiding the Cardinals to a 41-9 record from 2003-07. When he left to take the NFL job, there were plenty of people who felt he departed in a less than admirable way and had been constantly eyeing other jobs while he was there.

He infamously met with Auburn officials in 2003 to talk about taking the Tigers' head coaching job while Tommy Tuberville still had it.

But Petrino was greeted as a savior by Arkansas fans and has given them no reason not to admire and trust him since.

Until now.

Long said he didn't hear about the passenger - 25-year-old Jessica Dorrell, a former Arkansas volleyball player and current football program employee - until Petrino called him Thursday afternoon, minutes before a police report was released disclosing her presence at the accident.

Assistant head coach and linebackers coach Taver Johnson has been put in charge of the program in Petrino's absence. The former Ohio State assistant coach was hired in January.

Long's investigation could lead, based on conduct clauses in Petrino's contract, to a suspension or firing. While this case does not appear to involve any possible NCAA violations, Jim Tressel's firing at Ohio State last year showed that even a coach who won a national championship can lose his job for lying to his boss.

"I hope to have a resolution soon," Long said. "I certainly don't have all the answers here tonight, as we meet. But again, I have an obligation and responsibility to obtain the information and then act appropriately on that information."

The 51-year-old Petrino, who is married with four children, didn't mention he had a passenger during a news conference on Tuesday, two days after Sunday's accident, and a school statement that day quoted Petrino's family as saying "no other individuals" were involved. Petrino said then that he had spent Sunday with his wife, Becky, at a lake and was going for an evening ride. His only mention of Dorrell was vague, and without identification.

"When I came out of the ditch, there was a lady there that had flagged down a car," Petrino said Tuesday, nursing four broken ribs and wearing a neck brace to support a cracked neck vertebra. "The guy that was in the passenger's seat said, 'Get in, we'll just take you right to the hospital instead of waiting,' and so I got in the car and they headed toward Fayetteville."

In Thursday's statement, Petrino apologized and acknowledged that he had kept quiet about Dorrell.

"I have been in constant pain, medicated and the circumstances involving the wreck have come out in bits and pieces. That said, I certainly had a concern about Jessica Dorrell's name being revealed," he said. "In hindsight, I showed a serious mistake in judgment when I chose not to be more specific about those details. Today, I've acknowledged this previous inappropriate relationship with my family and those within the athletic department administration."

Dorrell, who did not return a call seeking comment, was hired March 28 by Petrino as the student-athlete development coordinator after serving as a fundraiser with the Razorback Foundation. She is in charge of organizing the recruiting process for the football team, including initial eligibility for each incoming player.

Long said he had not decided whether to suspend Dorrell.

Petrino signed a new seven-year contract in December 2010 after completing his third regular season at Arkansas. The contract, which was for an average of $3.53 million annually.

The police report said Petrino was riding with Dorrell when he lost control of his motorcycle. Dorrell said in the report that she wasn't sure what caused the accident, during which Petrino was unable to maneuver a turn and laid the motorcycle down on its left side while sliding off a rural, two-lane road about 20 miles southeast of Fayetteville.

Petrino said in the report that wind and sun caused the accident. The police report said Petrino and Dorrell were taken by a passer-by to an intersection in southeast Fayetteville, where a state police officer took Petrino to the hospital.

The police report said Dorrell wasn't taken to a hospital, and that she was dropped off at her vehicle, which was parked at the intersection. State police spokesman Bill Sadler said Petrino didn't try to hide Dorrell's part in the accident when questioned on Tuesday.

"Coach Petrino was as cooperative as anybody that we could ever hope to encounter following the traffic crash," Sadler said.

Petrino, who wasn't wearing a helmet, was hospitalized but had since returned to practice.

Arkansas has high expectations for next season, led by first-team All-Southeastern Conference quarterback Wilson. Also, Davis' return after missing all of last season with an ankle injury has only added to the high hopes.

How Petrino's misstep affects those hopes has yet to be seen. The next move is Long's.