When the final whistle blew on Saturday afternoon, the Harvard football team officially extended its unbeaten streak to nine with a 24-14 victory over visiting Lafayette.

The shrill sound meant that “Ten Thousand Men of Harvard” would soon fill the air, that postgame handshakes would commence, and that the Crimson could enjoy victory in a game that it led wire-to-wire.

But that final whistle marked something else as well, something much more significant. It meant that the real season was about to begin.

This year represents the third straight season that the Crimson has jumped out to a 5-0 mark. Harvard remains just one of five undefeated teams in the FCS. If you ask any player or coach, though, they will tell you that statistic means close to nothing.

Why? Because for the last two years, it’s been all about game six: Princeton. In each season, the Tigers defeated the Crimson, blemishing its then-undefeated record.

Sure, Harvard has been tested throughout the first five games of its schedule. The Crimson found itself trailing in the fourth quarter against Brown. Two weeks later, the team was locked in a scoreless tie at halftime against Cornell.

Harvard prevailed in both of those contests. But who could have possibly thought otherwise? Even for a pessimistic Boston sports fan, the Crimson represented a comfortable pick against the struggling Bears and winless Big Red. Matchups appeared even more favorable against Holy Cross, Georgetown, and, most recently, Lafayette.

The same cannot be said for next week. If the first five games served as a dress rehearsal, this Saturday is opening night and all of the lights are on.

It’s true that Princeton has two losses. And that quarterback and 2013 Ivy League Offensive Player of the Year Quinn Epperly was held out last week due to injury. But none of that matters. As we have seen with Princeton-Harvard, anything can happen.

In 2012, the Tigers scored 29 points in the fourth quarter to snatch a sure victory away from the Crimson. Last year, the two teams clawed tooth and nail before Princeton prevailed in triple overtime. If you’re looking for Ancient Eight drama, what more can you ask for?

Princeton will be the best team Harvard has played this season. So how did the Cambridge crew look in the tune-up for the game that carries the most Ivy League championship implications? It’s complicated.

Offensive consistency will need to improve. Against Lafayette, the Crimson finished three-of-16 on third down and went zero-of-seven in the second half. The fourth quarter saw Lafayette amass 171 yards to Harvard’s 12. That won’t fly next week.

The Crimson needs to consistently move the chains and refrain from giving Princeton a short field. Why? Only because the rapid-fire Tigers’ offense has averaged nearly 470 yards in the last two games against Harvard.

In addition, the Crimson can’t let its opponents hang around. Despite a number of second half chances, Harvard couldn’t grind down the clock or muster a knockout blow. If Lafayette hadn’t missed two field goals and dropped a touchdown pass, the score could have looked very different. While Harvard survived, a similar scenario on Saturday could prove suicidal.

Yet while offensive consistency was lacking, Harvard demonstrated its ability to explode with big plays against Lafayette. Each of the team’s three touchdowns were 30 yards or more, highlighted by a 79-yard score off a screen pass to junior wide receiver Andrew Fischer, who finished with 237 all-purpose yards. If there’s a remedy for failed third downs, it’s the explosive plays that fans just enjoyed at Harvard Stadium.

Regardless, the last two years of Harvard-Princeton have taught us to throw prior conceptions out the window. For three-plus hours this weekend, I will be expecting the unexpected.

The season may be halfway over, but the real games are just now beginning. From here on out, every Saturday represents a must-win situation.

But especially this Saturday. After all, it’s Princeton.

—Staff writer David Steinbach can be reached at david.steinbach@thecrimson.com.