Ohio State head coach Urban Meyer points at the red zone offense as an issue that needs to be evaluated. (0:26)

WEST LAFAYETTE, Ind. -- For weeks, Ohio State Buckeyes showed obvious flaws but found ways to escape and preserve a perfect record.

But when the Purdue Boilermakers dropped the hammer Saturday night, the second-ranked Buckeyes had no answers in a 49-20 loss, their second to an unranked Big Ten opponent in as many years, after they fell 55-24 at Iowa in November. Ohio State never led, committed 10 penalties, failed to score in the red zone on three of five opportunities and repeatedly caved on defense, allowing 539 yards, including 406 yards and five touchdowns to Purdue star freshman receiver Rondale Moore and senior running back D.J. Knox.

"The glaring shortcomings we have were exposed," Ohio State coach Urban Meyer said. "Number one, off the top, is our red zone offense. We go down there a few times, two field goals and one missed field goal. We've never had this issue. We're going to get a real thorough evaluation of that. And then the big plays on defense."

Meyer and players said that despite signs of trouble in previous games, they didn't see Saturday's struggles coming. Senior wide receiver Terry McLaurin said the team had its best week of practice entering the Purdue game.

"We didn't come in with a mentality, feeling like we had all these mistakes," McLaurin said. "We came in actually on a high note."

But the problems began right away, with a false start on the first play from scrimmage. Ohio State piled up yards but was one-dimensional on offense, as sophomore quarterback Dwayne Haskins attempted 73 passes, completing 49 for 470 yards. But the Buckeyes averaged just 3 yards per carry, and the offensive line repeatedly drew penalties to prevent the unit from finding rhythm.

"We missed some opportunities, had some penalties," Haskins said. "Our offense is all about timing and momentum, and we didn't do a good job of that today.

"What happened last year versus Iowa ... we can, we still make the Big Ten championship and do what we do to possibly make the playoff."

Ohio State has drawn 10 or more penalties in half of its games. The flags hit the Buckeyes in all three phases Saturday, including a roughing the punter foul on Davon Hamilton early in the third quarter that extended a Purdue drive, leading to a Knox touchdown.

"It's been an issue this year," Meyer said. "Not very disciplined. I think they're effort penalties, but just, I mean, ridiculous."

The Buckeyes entered the game among the nation's leaders in allowing plays of 20 yards or longer and 30 yards or longer. Knox had touchdown runs of 42 and 40 yards, while Moore had a 43-yard touchdown reception and repeatedly gashed the Buckeyes' defense.

"Tackling was a big thing tonight," safety Jordan Fuller said. "It's never just one thing. There's a bunch of things we have to get corrected."

Meyer said he remains confident that his coaching staff can make corrections in an open week before Ohio State resumes play Nov. 3 against Nebraska in Columbus. He said the open week will help Ohio State get healthier, especially in its defensive secondary, where several key players are hobbled.

Senior offensive tackle Isaiah Prince, who struggled Saturday with several penalties, addressed the team after the game. Another offensive lineman, Billy Price, spoke to the team after the Iowa loss in 2017. Ohio State went on to win the Big Ten championship and the Cotton Bowl while finishing No. 5 in the final CFP selections.

"Our program is prided on our O-line and D-line," McLaurin said, "so for somebody to step up like that and say something at a time like this, it's necessary. There's no pointing fingers. It's all about looking in the mirror and see what we could have done better.

"We got hit in the mouth, but it's about how you come back from it."