There were two plays that could have been the pivotal point in the game, the first one that would have been the deciding play if the Beavs had lost was the Brandin Cooks fumble in the 4th quarter. Oregon State had only begun to charge back and had just forced a punt after bringing the deficit to six points. The Aztecs had been forcing quick passes out of Mannion with pressure and drives looked like they would take several minutes. It was a screen pass to Cooks and he got a solid gain before a SDSU defender put his helmet on the ball.
At the time it felt like the end of the game, with the Aztecs getting such good field position and with how poor the defense has been all year, a touchdown seemed imminent. The defense did hold although they gave up one first down, but this was also important. If the Aztecs had scored a touchdown the momentum would have shifted back and the game might have gotten out of reach. The pick 6 might not have had the same effect with the scores where they were.
This did make the pick 6 from Steven Nelson the biggest play of the game. When the Beavs got the game to a 3 point deficit they needed a stop. The Aztecs played into this by being predictable and taking no risks. Or so they thought. After a first down run which was stuffed well in the backfield the Aztecs had a screen set up. The Beavers got into the backfield and pressured though and walk-on Aztec qb Quinn Kaehler did not handle the pressure very well and overthrew his receiver and right into the capable hands of Steven Nelson, who ran it back for a touchdown, although he probably could have walked in.
With that touchdown it completely flipped the positions and suddenly the Aztecs were chasing the Beavs and they had not been in that position all game. They had been running the ball and keeping the pressure off of their quarterback, but after that they had no choice to press, and they were unable to handle the moment. That one moment set all that up as the Beavers would have had to charge down the field to take the lead, if they were able to force a punt, but all those challenging circumstances were taken care of.
This had to be the most important moment of the game, it completely changed the complexion of the game and helped the Beavers escape with the victory although maybe undeserved.