By the numbers: Louisville's backfield struggles for yards

Brandon Radcliff, Louisville's leading running back, is averaging just 3.7 yards per carry. Jamie Rhodes/USA TODAY Sports

Louisville's best weapon on offense might be freshman Lamar Jackson, whose speed has made him one of the most effective running quarterbacks in the country. Despite only limited playing time against Houston and Clemson, Jackson has already tallied three 100-yard games on the ground, and his 435 yards rushing rank fourth among FBS quarterbacks. That's particularly impressive given that Louisville's offense wasn't designed around a running QB.

That's the good news. The bad news is that Jackson's success has largely covered up what is a glaring weakness among the Cardinals' running backs.

Take Jackson and the other quarterbacks out of the picture, and the numbers are bad.

Louisville's running backs are averaging 3.31 yards per rush, the third-worst rate in FBS.

Nearly a quarter of the Cardinals' carries by running backs end with a loss or no gain.

After recording four runs of 10 yards or more in the opener against Auburn, tailback Brandon Radcliff has just four more since.

For Petrino, the struggles are ubiquitous, particularly on the line.

"It's been a combination of everything -- of not being able to come off the ball and move the line of scrimmage and sustain our blocks and get onto the second level," Petrino said."

Indeed, the line has failed to do its job well, particularly up the middle. When running between the tackles, Louisville is averaging just 0.4 yards per rush before first contact on non-sack plays. Runners are getting hit at the line of scrimmage on virtually every carry. That's the worst rate among Power 5 programs.

On outside runs, the line has been a bit more successful (3.25 yards before contact, 29th in Power 5), but here the rushers have largely failed. Their 1.53 yards after contact rate ranks 63rd among Power 5 schools.

Overall, Louisville's running backs are mustering just 1.48 yards after first contact per rush, the worst rate in the Power 5.

Essentially Louisville has a backfield of downhill style runners and an offensive line that can't block the vertical running game. It's a serious concern.

"We've had issues with the exchange point, with the quarterback not being exactly where he needs to be, and then our running backs hitting their landmarks and getting yards after contact," Petrino said. "It's something we worked extremely hard on in the bye week.

Petrino said the team has worked on fundamentals, so the hope is that the Cardinals can find some more success this week. But the task won't be easy against a Florida State team that has looked much improved against the run this year.

In 2014, with apathy and inexperience plaguing the defensive line, the Seminoles allowed 80 runs of 10 yards or more. This year, they're on pace for 50. They've allowed just one rushing touchdown, and against a strong Miami running game last week, they surrendered just 20 yards on 19 carries.

Jackson remains a threat for Louisville, and one Petrino said he hopes will loosen up defenses for the other ball carriers. But Jackson is also less of a threat in the passing game than the Cardinals' alternatives at quarterback, which leaves Petrino to try trade one weapon for another. If Radcliff and Jeremy Smith can start making some noise on the ground, too, however, things could get a lot simpler for whichever quarterback is in the game, and Jackson's legs won't be the only thing putting fear into opposing defenses.