Harvard is not perfect. The Crimson coughed up the opening kickoff Saturday afternoon, their first turnover in four weeks, and handed the ball to visiting Princeton at midfield.
A little adversity for the 15th-ranked program in the FCS that hardly had been challenged through the first five weeks. They had outscored foes, 221-40, while extending their winning streak to 19 games.
Matt Koran and his mates on the formidable Harvard D, though, embraced the early opportunity to flex their muscles.
"We were kind of excited, honestly," said the 5-foot-11-inch, 210-pound senior captain, who teams up with classmates Jake Lindsey and Eric Medes to form arguably the best linebacking unit in the Ivy.
"We like being on the field first. As a defense, we react to adversity."
That included allowing a touchdown for the first time in four weeks — dating to a fourth-quarter score by Brown Sept. 26 — a stretch covering 220 minutes and 30 seconds on the game clock. But after John Lovett finished off Princeton's second-quarter, game-tying, 11-play, 70-yard march with a 2-yard flip to Nick Peabody for a 7-7 game, Harvard shut the door, emphatically.
On his way to a career-best 437-yard passing performance, senior Scott Hosch (29 of 40, 2 TDs) drove the Crimson 94 yards for the go-ahead score with 53 seconds left in the first half of an eventual 42-7 runaway over the Tigers in front of 17,444 at the Stadium.
That momentum-shifting TD, a 5-yard connection from Hosch to Ben Braunecker (seven catches, 133 yards) in which the QB rolled to his left, stopped, spun right, then zipped a pass across the field to his senior tight end who was on the ground after a slip, was the trigger for an attack that piled up 647 total yards.
"We kept moving the ball the entire first half, but we kept shooting ourselves in the foot," said Hosch, now 12-0 as a starter. "We kept saying in the huddle, we have to finish, we have to finish."
The Crimson (6-0, 3-0) then put the game out of reach after the break, converting their first four possessions into 28 points, with shifty senior Paul Stanton (18 carries, 119 yards) punching in scoring runs of 2 and 9 yards and the fleet-footed Andrew Fischer (10 catches, 190 yards) making a dramatic return to the lineup after sitting the past two weeks with an upper-body injury.
"The touchdown at the end of the half gave us a lot of momentum," said Harvard coach Tim Murphy, after watching his normally sure-handed squad put the ball on the ground four times in the first 30 minutes, losing two fumbles.
"And the kids came out really, really hard in the second half and played with a lot of conviction."
Princeton coach Bob Surace said the "first 27, 28 minutes, we played very good football. Probably should have been a 9-6 game, we popped the ball out, and it's in our hands, and we just didn't recover it, I guess.
"From that point on, we were not exact enough . . . then they got that swarm of points on us, and it made for a long second half."
Koran and Lindsey (nine tackles apiece) spearheaded a defense that yielded 55 yards on the ground. And for the 50th time in Murphy's 22-year tenure, covering 215 games, Harvard held an opponent to 7 points or fewer.
"It is kind of uncharacteristic for our defense to give up touchdowns, so when it happens, we take it pretty seriously," said Koran.
The Crimson were also suiting up at home for the first time since the death of 2013 graduate D.J. Monroe, a two-time all-Ivy cornerback who was killed commuting to work in Florida Oct. 13.
They will don "DJM36" decals on their helmets for the remainder of the season to honor their fallen former teammate.
Their challenging late-season Ivy slate continues Friday night, when 25th-ranked Dartmouth (6-0), off its best start since a 10-0 run in 1996, makes a visit. "The best team we will have faced," said Murphy.
Craig Larson can be reached at clarson@globe.com. Follow him on Twitter @GlobeLars.