CHESTNUT HILL — It was midway through a marathon intrasquad scrimmage inside Alumni Stadium, and Boston College’s new head coach was fuming.

The Eagles’ first-team offense, led by junior starting quarterback Thomas Castellanos, had just allowed a sack on the opening play of a drive. One play later, a lineman was whistled for holding during a Castellanos scramble. Next play, same story: scramble, flag, hold.

Bill O’Brien, whose ferocious temper earned him the nickname “Teapot” during his years as a Patriots assistant, didn’t hide his frustration.

“It was, like, third-and-52,” O’Brien lamented after practice. “I’m not sure I’ve ever been in a third-and-52. I’ve been a third-and-48, but never a third-and-52. That was kind of new to me. Not sure what play to call there. But that’s what penalties do to you. We’ve got to be a more disciplined team.”

Calling O’Brien’s new job a metaphorical third-and-52 would be an overstatement. But it’s at least a third-and-long.

BC football has not finished a season ranked in the AP Top 25 since 2007, Matt Ryan’s senior year. It peaked at mediocre under each of its last three head coaches (Frank Spaziani, Steve Addazio and Jeff Hafley) and hasn’t posted a winning record in ACC play in 15 years.

Last season, the Eagles reeled off a five-game win streak, came within a few plays of upsetting No. 3 Florida State and won their bowl game. But they also nearly lost to FCS neighbor Holy Cross at home, finished tied for ninth in the ACC standings and were severely lacking in several key areas.

They ranked 82nd in the FBS in scoring offense and 87th in scoring defense. They were awful at defending the run (121st in yards allowed per game) and boasted a scattershot passing attack (108th in yards per game; 103rd in completion percentage). They threw 14 interceptions and grabbed just eight, five of which came courtesy of cornerback Elijah Jones, who now plays for the Arizona Cardinals. The Eagles also ranked 101st in penalties committed — a problem that’s persisted into this summer.

The right man for the job

BC flirted with respectability at times during Hafley’s four-year tenure but never reached it. After Hafley bolted in January to become the Green Bay Packers’ defensive coordinator, folks at The Heights are hoping local guy O’Brien can be the one to finally return the once-proud program to prominence.

He believes he can.

“Boston College, it’s already an unbelievable academic school. It’s got a beautiful campus 15 minutes from downtown Boston. Why can’t we be good at football?” O’Brien said, repeating the sales pitch he’s spouted often since taking the job. “But there’s a standard. We have to play disciplined football. We have to play smart football. We can’t play football where we hurt the team. We can’t be selfish. We have to be good teammates.

“We have to understand what it takes to be a good football team, and I think we’re on our way. I really do. But Boston College can be good at football. We’re trying to build that every day by repeated actions.”

An Andover native who played at St. John’s Prep and collegiately at Brown, O’Brien offers a rare blend of area awareness and high-level experience that made him an ideal hire for athletic director Blake James.

Outside of his two stints running the Patriots’ offense under Bill Belichick — the first highly successful, the second much less so — the 54-year-old also made the Houston Texans a perennial playoff team, revived Penn State’s football program in the wake of the Jerry Sandusky scandal and helped groom Bryce Young into a Heisman Trophy winner and No. 1 overall draft pick at Alabama.

“You’re talking about a guy that every time I walk into the building,” quarterbacks coach Jonathan DiBiaso said, “down the hall is a resource of a guy that coached Tom Brady, coached Deshaun Watson, coached Bryce Young, was the head coach at Penn State in a really tough situation and turned that program around, was very successful in the NFL as the head coach of the Texans, as a coordinator for Bill Belichick and Nick Saban — two of the best coaches all-time.”

Leading a staff that features both newcomers and Hafley-era holdovers — DiBiaso, Salvon Huggins (running backs), Darrell Wyatt (assistant head coach/wide receivers), Matt Applebaum (offensive line) and Matt Thurin (special teams) all were with the team last season — O’Brien has preached a message that will sound familiar to Patriots fans.

“I’ve always had a firm belief in what he believes in, as well, (which) is being a tough, physical, disciplined football team,” offensive coordinator/tight ends coach Will Lawing said.

Added DiBiaso, a former star QB at Everett High School: “He talked when he first got here about the Patriot Way that he had learned, which is don’t let the people around you down.”

Pieces for the rebuild

Lawing, who’s worked under O’Brien every season since 2013, is one of just two staffers who followed him to BC from the Patriots organization. The other: Belichick’s longtime right-hand man, Berj Najarian, who’s overseen a near-complete overhaul of BC’s football operations department in his role as chief of staff.

The product on the field also will be a blend of fresh and familiar.

Castellanos headlines a long list of returning starters — 15 total, including top receiver Lewis Bond, running back Kye Robichaux and at least three starting O-linemen. Offensively, those will be supplemented by a handful of impact transfers, most notably former Kansas State/Florida State back Treshaun Ward, wideouts Jayden McGowan (Vanderbilt) and Jerand Bradley (Texas Tech), and tight end Kamari Morales, who caught passes from Drake Maye at North Carolina.

Redshirt freshman Reed Harris — a fast, physical, 6-foot-5 receiver from Montana — also looks like a potential starter, and Xaverian product Danny Edgehille has a chance to contribute at tight end as a true freshman behind Morales and returning starter Jeremiah Franklin.

Those additions should give Castellanos a more talented stable of pass-catchers and, coaches hope, make BC’s offense far less reliant on its productive ground game. Castellanos was one of just two FBS QBs to pass for 2,000 yards and rush for 1,000 in 2023 (Jayden Daniels was the other), but only three players threw more interceptions than his 14 despite BC ranking 96th in pass attempts per game.

O’Brien’s history of coaching up top-tier signal-callers will be a major asset, too.

“He has a lot of experience with not just quarterbacks, but the game of ball,” Castellanos said. “So just me learning from him has been really great for me.”

On the other side, the strength of the defense should be its experienced front four of ends Donovan Ezeiruaku and Neto Okpala and tackles Cam Horsley and George Rooks. Transfers Bryquice Brown (Georgia State), Ryan Turner (Ohio State) and Cameron Martinez (Ohio State) will be players to watch in a new-look secondary.

With O’Brien’s old team down in Foxboro expected to struggle this season, there’s room for BC to carve out a larger foothold in the New England football landscape if the Eagles impress early. That won’t be easy, though. Two of their first three games are against teams ranked 10th (Florida State) and 11th (Missouri) in the preseason AP poll, starting with a primetime season opener in Tallahassee on Labor Day.

“I think everyone understands what type of environment that’s going to be,” O’Brien said, “and we’re looking forward to it.”