The Big Ten has started a trend — albeit a small one — by hiring former NFL coaches in an attempt to lead two of their programs back to glory. Illinois’ hiring of Lovie Smith earlier this month followed what Michigan did when it brought in former Wolverines star Jim Harbaugh to clean up the mess left behind by Brady Hoke.

The Harbaugh move was not a surprise, and neither should be Illinois’ decision. Believe it or not, the Fighting Illini gig is now the seventh college football job for the 57-year-old Smith, who was Kentucky’s linebackers coach in 1992 and coached defensive backs for Tennessee in 1993-94.

So are these Big Ten hirings good moves or bad ones? Harbaugh has already made an impact — his Wolverines made a 5-win improvement from 2014 to last season — but the jury is obviously out on Smith, who is a college head coach for the first time after compiling an 89-87 record as an NFL head man, including one Super Bowl appearance with the Chicago Bears.

Smith, who was fired by the Tampa Bay Buccaneers, is one of just five former NFL head coaches now head men in college. Nick Saban, Mike Riley, Jim Mora and Harbaugh are the others.

Coincidentally, each member of that quality on-campus quartet struggled as an NFL head coach. But each has also bounced back to succeed in school, with Saban leading the group by winning four national championships in seven seasons since leaving the Miami Dolphins to coach Alabama.

Jimmy Johnson, Barry Switzer and Pete Carroll won college national championships and Super Bowl rings, but their NFL success makes them exceptions.

Most former NFL coaches who went back to college got much better grades than they did in the pros.

Following 12 incredible seasons with the Florida Gators that included a national title in 1996, Steve Spurrier bounced back from his two terrible years with the Washington Redskins to lead South Carolina to three consecutive 11-2 campaigns before he resigning last year.

Like Spurrier, Saban — who went 15-17 while coaching the Dolphins — has sandwiched a pair highly successful stints in college around his two years in the NFL.

Riley, 14-34 in three seasons with the San Diego Chargers, is 99-87 in college following a couple of stints at Oregon State and his first season with Nebraska. Mora is 37-16 in three seasons with UCLA after going just 31-33 in four seasons with the Atlanta Falcons and Seahawks.

Bobby Petrino is another example of a former NFL coach who should have stayed in school. Petrino, who is 100-39 following two stints at Louisville along with stops at Arkansas and Western Kentucky, flew the Falcons’ coop after going just 3-10 in his only NFL head-coaching gig.

Lou Holtz went a Petrino-like 3-11 with the New York Jets in 1976. But the College Football Hall of Famer was 249-132-7 on campus, including his stints with Arkansas and South Carolina.

Butch Davis, Dennis Erickson, Frank Kush, Bud Wilkinson and Dick MacPherson are other examples of successful college head coaches who flopped in the NFL. Tom Coughlin is the epitome of someone who bucked that trend.

Coughlin parlayed a 21-13-1 three-year run at Boston College into a successful NFL head-coaching career with the Jacksonville Jaguars and New York Giants, from whom he resigned in January. Coughlin, 69, is still energetic and exuberant, but he might be too old for a university to take a chance on him.

So, yes, the NFL has been a good place to find college head coaches. But for the most part, those coaches flunked in the pros after successful tenures in school before and after their pro days.

New Illinois AD Josh Whitman, who fired Bill Cubit and hired Smith within a three-day period, is pinning his hopes on someone who is finally the big man on campus for the first time. For now, he feels that Smith — who received a 6-year, $21 million deal that could grow to $29 million — will pass this test with flying colors.

“Lovie’s going to be a great recruiter,” Whitman told the Associated Press. “There’s not a living room in America that’s not going to open up their doors to Lovie Smith and his coaching staff.”

If that turns out to be true, athletic directors from other Power 5 conferences might imitate the Big Ten’s trend of hiring former NFL field generals. At the very least, it would give canned NFL coaches another option besides joining brethren such as Bill Cowher, Mike Ditka and Herm Edwards among the ranks of TV analysts.