Florida State football's narrow 31-29 win over Boston College on Saturday left its defense exposed, to say the least.

Up 31-10 in the third quarter, the Seminoles allowed 19 straight points, putting them on upset alert up until the final minute of the game.

After Saturday's game, according to the NCAA, FSU's defense ranks 101st in the country, allowing 1,174 yards of offense on 201 plays for an average of 391.3 yards per game. Against Boston College, FSU allowed 305 passing yards, 190 rushing yards and three touchdowns.

Struggling to get stops

FSU's Achilles heel came in defending third-down and fourth-down conversions. The Eagles were 8-19 on third down and 4-5 on fourth down.

This included a third-and-17 situation that BC quarterback Thomas Castellanos converted on, eventually leading to a touchdown.

"Yeah, I mean, there wasn't really a common (denominator). There was an unbalanced scramble, there was a counter run on a third and extra long, and there were a couple of quarterback draws in there," FSU defensive coordinator Adam Fuller said.

"It's just tying it all together. The ball found the mistakes and that's something that you continue to harp to your group and you continue to harp to the individuals of mistakes need to be addressed and cleaned up and we did it and so now we've got to go play better."

The Seminoles allowed 12 "chunk plays," resulting in 348 yards and one touchdown on those plays.

FSU also relied heavily on its first team having to play the majority of the game, and it struggled as well. Jared Verse struggled with his tackling grade (33.9) and overall posted just a 63.7 defensive grade, according to Pro Football Focus. He also missed two tackles.

Linebacker Tatum Bethune's tackling graded out at 48.7, missing two tackles. Fellow linebacker Kalen DeLoach had a 51.2 tackling grade and missed one tackle. Defensive back Kevin Knowles II had a team-low 33.9 tackling grade, missing three tackles. He led the secondary in snap counts with 67.

"We had some guys play their most reps they played this season," Fuller said. "It wasn't something they hadn't done before in their career, but I think all those moments of whether it was a mistake or whether it was playing more reps, it's all part of them taking all that information and putting it to this week."

"We don't want to play a lot of plays, but sometimes that happens if you don't execute on third down. That's usually the message."

Chasing the rush

Castellanos was an issue for the Seminoles as well. He was an X-factor for BC's offense, passing for 305 yards and two touchdowns. When he was unable to find his receivers, he rushed for 121 yards and a touchdown. He was a mobile threat FSU was all too familiar with.

"He's a shifty runner, but we've seen quarterbacks like that in the past. I think when you're playing and as the game gets going and you start giving the information, " Fuller said. "Then it creates another issue. Give credit, the way college football has gone now, you're getting a lot of good players behind the center and they have options, whether it's to keep it, to throw it, to run quarterback draws."

"When you're playing, you've just got to make sure that whatever the weakness of each call is, guys understand it and still get their job done and then be able to tilt it the other way when you need to."

Struggling against the 69th-ranked offense in the country before facing Clemson, whose offense ranks 20th in the country, raises red flags for the Seminoles.

The Tigers have the third most first downs in the country (86), the 15th-best rushing offense in the country (216 yards per game), and the 20th-best scoring offense in the country (121 points, 40.3 per game). On the road in Death Valley, the defense needs a major response.

When it comes to the dominance on the rush, Fuller highlighted what running back Will Shipley has done for the Tigers this season. In just three games he's already rushed for 225 yards. Last season against FSU he recorded 121 yards in a 34-28 win in Tallahassee.

"They've got a really good running back. I think he's done a really good job of just breaking tackles. He's aggressive, I think he's a really good pass-catcher," Fuller said. "I know he probably hasn't had the success that he's wanted yet, but we've seen him at his best and he's a really good player."

GAME INFORMATION

Who: AP No. 4 FSU (3-0, 1-0 ACC) at Clemson (2-1, 0-1)

When/where: Saturday, Sept. 23, noon.; Memorial Stadium, Clemson, S.C.

TV/Radio: ABC/94.9 FM

Live game updates: www.Tallahassee.com; @Ehsan_Kassim on Twitter; @jackgwilliams on Twitter; @JimHenryTALLY on Twitter

Jack Williams covers Florida State athletics for Tallahassee Democrat. Contact him via email at jwilliams@tallahassee.com or on Twitter @jackgwilliams.

This article originally appeared on Tallahassee Democrat: Adam Fuller speaks on FSU football's defensive lapse against Boston College