A year after Dan Enos left a head coaching job at Central Michigan to become the offensive coordinator at Arkansas, Pete Lembo made a similar MAC-to-Power Five move, going from head coach at Ball State to assistant at Maryland.

About a month later, Southern Mississippi coach Todd Monken left the Golden Eagles of Conference USA to become the offensive coordinator for the NFL's Tampa Bay Buccaneers.

Behind each switch were myriad motivations: money, long-term security, family, friendship, professional growth. No two coaching moves are exactly alike and three do not necessarily represent a trend.

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The moves do raise a question: Is the widening revenue gap between schools in the Power Five conferences and the smaller Group of Five schools making it more difficult for those smaller schools to hire and retain quality coaches?

Daniel Parker from Parker Executive Search, one of the most frequently used search firms in college sports, said at the very least the list of potential candidates has changed for many Group of Five schools.

''When I did a MAC job, I could go get a coordinator from a Power Five school,'' Parker said. ''If you're doing Georgia State, you could look at coordinators from Georgia or Georgia Tech. Now those guys make a lot of money. People aren't willing to take that kind of pay cut. Now you've got to get creative.''

The revenue difference is clear: Conference television networks, billion-dollar media rights deals and the College Football Playoff payoffs are streaming into Power Five schools, which are generally taking in about 30 times what Group of Five schools do annually.

According to USA Today's salary database - which does not include a few private schools - nine coordinators in the Bowl Subdivision last season made more than $1 million last year. Eighty-one assistants made more than $500,000, including several position coaches.

Meanwhile, 34 head coaches, all in Group of Five conferences, made less than $700,000.

Of the 71 head coaches making more than $1 million per year in 2015, only 12 were working outside the Power Five - and of those only Louisiana Lafayette's Mark Hudspeth was working in the Sun Belt, Conference USA or Mid-American Conference.

When Enos left Central Michigan he was making $350,000 per year. He made $200,000 more than that last season running Bret Bielema's offense at Arkansas.

''Is the pool (of candidates) getting smaller? I think it's fair to say that because of the dollars one makes as a coordinator,'' said Toledo athletic director Mike O'Brien, who promoted offensive the Rockets' own offensive coordinator, Jason Candle, when coach Matt Campbell left for Iowa State.

Toledo tried to keep Campbell with an offer to make him the highest paid coach in the MAC that would have pushed his salary to around $1 million per year. Iowa State, with a $70 million athletic budget that is one of the lowest in the Big 12, gave Campbell a six-year contract with a starting annual salary of $2 million.

In Lembo's case, money wasn't the issue as much as opportunity and experience. He took a six-figure-per-year pay cut to become Maryland's special teams coordinator and assistant head coach to 38-year-old DJ Durkin, a first-time head coach.

Having gone to school nearby at Georgetown, Lembo had friends and family in the area. The move from Muncie, Indiana, to College Park, Maryland, cut the distance between him and his parents in Raleigh, North Carolina.

And Maryland also provided Lembo the chance to fill a hole on his resume that was becoming increasingly glaring. The Power Five football programs are becoming massive operations and athletic directors are increasingly leery about turning them over to coaches without that kind of experience.

In 23 years as a college football coach, including the last 15 as a head coach with a record of 112-65, Lembo had never coached at a Power Five school. He is now getting hands-on experience in that world.

''At Ball State, we had four full-time academic people for the entire athletic department, one of which that just worked with the football team,'' Lembo said. ''Here at Maryland we have six full-time academic support people that just work with the football program.''

Southern Mississippi coach Bill McGillis was faced with hiring a coach a little more than a week before signing day when Monken left to become offensive coordinator for his friend and new Bucs head coach, Dirk Koetter.

McGillis landed on Jay Hopson, a former Southern Mississippi assistant coach who led FCS Alcorn State to consecutive Southwestern Athletic Conference championship games. Hopson received a contract that pays him about $500,000 per year, about $200,000 less than Monken made last season.

McGillis rejects the idea that the widening gap between P5 and G5 is significantly changing the way coaches come and go.

''The market was what I hoped it would be and I would also tell you that there were coaches, coordinators making well into seven figures - I'm talking north of a million dollars - that reached out and expressed interest in our job,'' he said. ''I do think that because of the number of coordinators that are now between a million dollars and two million dollars, there's a handful - it's probably on one hand - that may be off the table.''

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Follow Ralph D. Russo at www.Twitter.com/ralphDrussoAP

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AP College Football: http://collegefootball.ap.org