After running in two scores against Bucknell and passing for two more, including a thundering 59-yard toss to teammate Kyle Juszczyk, senior quarterback Colton Chapple will lead the Crimson offense against Princeton on Saturday.

What a difference a year makes.

This time last season, the Princeton football team was 1-4 and on its way to a second-straight 1-9 finish. Over the course of the year, the Tigers gave up the second-most points in the Ivy League and scored the fewest.

But that Princeton team shares little in common with the Tigers squad that has come to play in the first five games of 2012. Princeton brings its first three-game winning streak since 2006 (the last year they won an Ivy crown) and an unblemished conference record into Saturday’s home contest against Harvard.

“This is what I expected, absolutely positively,” Crimson coach Tim Murphy said. “We expected them to bust out, it was just a matter of time.”

Predicted to finish last in the preseason Ivy League poll, the Tigers started the season with a three-point loss to Lehigh, which is currently ranked seventh in the FCS. In Week Two, Princeton lost to Georgetown on a field goal with 14 seconds to play after the Hoyas got into field goal range thanks to a third-down roughing-the-passer penalty on the Tigers and a fourth down conversion.

But then things changed radically.

Princeton finally ended its losing streak the following week with a 33-6 romping of Columbia. That win started a three-game winning streak that is more indicative of the talent the Tigers put on the field, according to a coach who knows a thing or two about winning streaks.

“It’s just mind-boggling that they could go 2-18 with the incredible talent they’ve had on that team,” Murphy said. “In my 18 years here, they’ve had more talent than anybody, including Harvard, so this is what I expected.”

Much of Princeton’s success can be attributed to a dominant defense that gave up just 20 points during its three-game winning streak, including a shutout of Brown last week.

“They are huge and athletic, and they now are in sync,” Murphy said. “They understand what they are supposed to do in that defense; it’s just all come together, and now they believe.”

Princeton’s D is led by a pair of defensive ends in their 3-4 scheme that wreak havoc on opposing offensive lines.

“You start with the two bookends,” Murphy said, “300-pound NFL prospect Caraun Reid, easily the best defensive lineman in our league, [and Mike] Catapano—probably the second best defensive linemen in the league on the other end.”

Those two are third and first in the conference in sacks, respectively, but they are far from the only gifted defensive players on the Tigers’ roster.

“You don’t even talk about the 290-pound nose guard,” Murphy said. “They don’t talk about the 6’4”, 260-pound [strongside] linebacker, the 6’2”, 240-pound [weakside] linebacker. They are just huge and athletic.”

Senior quarterback Colton Chapple will need to maintain his recent level of play, but his coach said he will also need a consistent running game to help him a week after senior running back Treavor Scales gained just 2.7 yards per rush against Bucknell.

“The bottom line is you have to stay balanced,” Murphy said. “If you come out and throw the ball 75 times, then eventually they will get to their quarterback, so you have to somehow keep them off balance.”

Scales said he’s ready to take on the Tigers’ defensive line after battling one as good in practice.

“They have some studs out there,” Scales said. “But I know for a fact that we have some studs too, so I practice against guys of their caliber every single day of my life.”

Those Harvard studs are part of a defense that ranks second in the league in total defense and points allowed, behind Princeton in both categories. But the Crimson defense is expected to have the upper hand Saturday as the Tigers are seventh in the league in total offense, while Harvard is first.

“The last two years they weren’t statistically a great offense,” Murphy said. “But we not only haven’t stopped them, we haven’t slowed them down the last two years, so that’s a big challenge to our defense. “

Princeton put up 39 points in last year’s loss and 28 the year before, both of which were highs for them against Ivy opponents.

Given the success the Tigers’ offense has had against the Crimson in recent years combined with how well their defense has performed this year, Saturday’s matchup could pose the biggest challenge yet for a defending-champion Harvard squad that has rolled to five straight wins by an average margin of victory of nearly 28 points thus far this year.

“I don’t know if any of us could have looked at the Princeton game based upon their record…as going to be a or the pivotal game, but clearly it is,” Murphy said.

Beyond being the most talented Ivy squad according to Murphy, the Tigers will be one of the most motivated as well this weekend thanks to their undefeated conference record and a senior class that has not beaten their Cambridge-based nemeses.

“Their level of motivation could probably not be any higher,” Murphy said. “As our players put it, they will be geeked up to play.”

—Staff writer Jacob D. H. Feldman can be reached at jacobfeldman@college.harvard.edu.