I had to go in and do what the coaches wanted me to do and play as hard as I could out there," Lopez said. "You get thrown in there right away out of nowhere.
"It is kind of hard and kind of tiring, but after a couple series I got used to it and just have to go out there and play as hard as I can."
Lopez was ready when his name was called and much of that has to do with simply being a better player than he was at the start of the season.
"I think my main improvement is all of the mental things," Lopez said. "Learning the tendencies, what we are doing out there, knowing what everyone else is doing so I know where I have to be all of the time on defense."
Attention now turns to UCLA and Lopez does not try to hide his belief that this game is as important as they come.
"This is definitely one of the biggest games," he said. "Obviously Oregon was big, but this is the biggest game of the season. The way we have played against UCLA these last couple of years, we want to go in there and beat these guys and keep it at one loss for the rest of the year."
In addition to staying in the race for the Pac-12 South, Lopez has extra motivation because he was a freshman when Arizona traveled to the Rose Bowl and lost 66-10.
"I went my freshman year," Lopez said. "It’s definitely not one of my fondest moments, but I feel this game is going to be much different than that game and even last year.
"This is one of those where you bring up the last time we were there because it wasn’t a good game and all of us are now physically and mentally prepared for this one more than we were for the game two years ago. I know we are going to go in there and play our hardest and hopefully come out with a win."
It won't be easy, however, as Lopez knows that the Bruins have plenty of talent on offense.
"They have talented players," he said. "Brett Hundley is a great quarterback and he can move, throw the ball. The receivers are talented and physical blockers. Paul Perkins runs the ball well and the offensive line is very good.
"This is a good team, so we have to be prepared for them. There’s nothing better than these types of games. You always want to play games like this and when you get the opportunity it is the greatest feeling."