Throughout the course of a year, individual plays stand out, defining a football teams' successes and failures.
Through four games, USC's already had its share.
The season changed when Mark Sanchez fell to the turf at Howard Jones Field, dislocating his kneecap. The injury set the stage for the emotional bump the Trojans got when he returned to the field in their opener.
There was Damian Williams finding the end zone twice and Joe McKnight gashing the Ohio State defense and Rey Maualuga taking a pass the other way in the game of the year that was compelling for all of about a quarter.
And after Jacquizz Rodgers scooted his way past the USC defense at Oregon State, the Trojans really had their backs pressed against the wall.
They needed to do something defining against Oregon, and they did just that.
Like Oregon State had done the previous week, the Ducks took the game's opening kickoff and marched down the field.
Oregon went 70 yards on 14 plays, running up the middle of the field just like the Beavers had done the previous week, using some foolish penalties to get in the end zone and take a 7-0 lead.
At Oregon State, the Trojans (3-1, 1-1 Pac-10) failed to take back any of the momentum, failing to pick up a short third down, forcing the defense to go back on the field in the blink of an eye.
Against the Ducks, though, the Trojan offense put together one of those moments that could turn the season.
"We couldn't get punched in the mouth again," running back Stafon Johnson said. "That's what happened at Oregon State. They scored and we went three-and-out, putting more pressure on the defense."
Instead of meekly punting after just three plays, the Trojan offense took the ball and moved down the field. Even though the Trojans managed just a field goal after getting inside the Oregon 10-yard line, the message was sent.
"We needed that drive. We didn't want to have a repeat of what happened last week," C.J. Gable said. "We were able to drive and get down the field. We'd have rather gotten a touchdown, but at least we got on the board."
Defensive Kyle Moore said the points got the defense fired up.
"Our offense didn't fall flat," he said. "They came out and scored. It gave us confidence."
And more importantly, it gave the defense time.
Against Oregon State, the Trojans ran a little over 2 minutes off the clock before sending the defense back on the field. Saturday against Oregon (4-2, 2-1), they took 5:13 off the clock, plus the commercial time after the score.
The time was used wisely.
"We brought the whole defense up," Moore said. "Usually we keep it in positions, but after they scored, we brought everyone together to fix some things. We came out and we executed the next time.
"We made adjustments early."
Oregon showed its hand early, using counter plays in the running game, something the Ducks hadn't shown on film.
Instead of slanting their defensive line towards the run, the defense stayed home and got off blocks, shutting down the Ducks running game.
"Our coaches did a great job of seeing what we had to fix," linebacker Brian Cushing said. "Adjustments were huge for us tonight. Luckily, we had time to make some and slow down such an explosive team."
The USC defense came back on the field and stopped Oregon repeatedly for the rest of the game while the offense made big play after big play.
The two units created momentum for one another, Johnson said.
"Just like we were trying to make a statement, the defense was too," he said. "They had it in mind, and they responded quickly.