In the weeks before the season, Boston College football players spoke enthusiastically about coach Bill O’Brien’s infectious confidence.

Instead of adopting an underdog mentality like in previous years, the Eagles emphasized the mindset of a heavyweight.

“It’s more competitive, more like we’re going to get it done,” quarterback Thomas Castellanos said. “It’s not about we’ll win if we do it or when we do it. It’s about we’re going to win. That’s the kind of coach you want to play for.”

That change was evident in training camp and even more so when the Eagles dismantled No. 10 Florida State 28-13 in the season opener on Monday night in Tallahassee. BC had lost 12 of 13 games against FSU and hadn’t beaten a top-10 team in a decade, but none of that mattered.

The Eagles were convinced they were the better team, and when the game began, it was clear why. They overwhelmed Florida State in the trenches, played disciplined football, and didn’t let the situation get too out of hand.

“We’ve been building confidence all summer,” running back Kye Robichaux said. “We’ve been working hard. It’s been a real struggle. You can see the bond within the team. It’s just a whole bunch of dogs, man, dedicated to one goal.”

Here are five takeaways from this convincing triumph:

1. Discipline is a cornerstone of O’Brien’s approach.

Throughout training camp, O’Brien rarely chastised players for physical mistakes, but when a player made a mental mistake, he didn’t hold back.

The Eagles were polite about the constructive criticism, trusted O’Brien’s experience and were convinced that their daily improvements would pay off.

“He’s very honest and truthful,” guard Ozzy Trapilo said. “Sometimes the truth is hard. He’s not afraid of it. I think that’s a benefit to the guys on the team.”

When the Eagles played Florida State last year, they were the more explosive team, but a program-record 18 penalties marred an otherwise promising performance. And that highlighted a larger trend that the Eagles often get in their own way.

Third-and-longs became the norm, winning the battle for possession was anything but a given, and tackles in the open field were sporadic.

On Monday night, the Eagles were far more disciplined, prepared and smarter, hitting 9 of 16 third downs and holding the Seminoles to 3 of 14. They committed just one foul compared to seven for FSU, won the turnover battle 1-0 and managed to avoid any puzzling moments.

2. The offensive line has the chance to be something special.

During their five-game winning streak last year, the Eagles relied heavily on their offensive line, systematically wearing down their opponents well into the fourth quarter.

Monday’s game followed a similar pattern, as they dominated possession from 39:09 to 20:51. BC allowed FSU only 51 seconds of possession in the first quarter and never let the Seminoles settle in their home stadium.

Jude Bowry (left tackle), Dwayne Allick (left guard), Drew Kendall (center), Jack Conley (right guard) and Trapilo dominated FSU’s defensive line, which had received much praise at the start of the season.

Granted, this FSU team may not have quite as much firepower as many expected, but BC’s offense was still commendable. The Eagles managed 263 yards on the ground compared to just 21 yards for FSU and dominated the offensive line.

Robichaux (19 carries, 85 yards, 1 TD), Treshaun Ward (12 carries, 77 yards), Castellanos (14 carries, 73 yards, 1 TD) and promising freshman Turbo Richard (4 carries, 28 yards) all made room with ease.

“Our running back room is as tight as it can be,” Robichaux said. “We all benefit from each other.”

3. Castellanos has changed his approach slightly.

The more chaotic a piece is, the more likely Castellanos is to make something out of nothing.

Although he showed off his agility on Monday, he played with more composure and took fewer risks than last year. It’s clear that O’Brien and quarterback coach Jonathan DiBiaso have been preaching the importance of valuing the ball and not giving the opponent opportunities.

Castellanos made mature decisions, read the right lines and made life easy for his receivers. He finished the game 10 of 16 passing for 105 yards and two touchdowns, excelling in a pro-style offense that BC used last year.

“I thought he managed the game very well,” O’Brien said.

4. You mastered the ups and downs without any problems.

The first 24 minutes belonged to BC. Florida State looked out of form and did not record a first down until 6:13 into the first half.

BC took advantage and built a 14-0 lead, then FSU was able to close in. The Eagles stymied two promising drives late in the half, holding the Seminoles to field goals each time.

Early in the second half, BC forced FSU into a fourth-and-5 attempt on their own 47-yard line. The Seminoles decided to go for it, but quarterback DJ Uiagalelei sent a special throw like a gift right into the hands of BC defensive back Max Tucker.

“That was probably one of the most important plays of the game,” O’Brien said. “It really got us going in the second half.”

BC extended its lead to 21-6 on a 4-yard pass from Castellanos to Robichaux. When FSU cut the lead to 21-13 with 5:19 left in the third quarter, the Eagles responded immediately when Robichaux scored from 2 yards out four minutes later.

“That was a drive we had to respond to,” O’Brien said. “They were on a roll. That kind of drive is great.”

The Eagles didn’t let anything go wrong in the fourth quarter. This is a mature, experienced team that knows how to finish games.

5. It is a great victory, but it is only a victory.

O’Brien then overwhelmingly said that while this was a big step for the program, it was just the beginning.

It goes back to his philosophy of expecting a win. The Eagles celebrated, but they didn’t overdo it. That was part of the plan, and the first step has been taken.

“This is a very important win for BC and for our current situation,” O’Brien said, “but it’s just one game.”