The Gunners defeated Los Che 4-2 on Thursday night, winning the tie 3-7 on aggregate.
"You can't say conceding seven goals in two games is unfair."
"The first goal gave us a lot of encouragement," Rodrigo went on. "But we conceded five minutes later.
"Every goal they scored made it more difficult for us. They have very good players upfront and and are a very consistent team.
"I hope people can see we were always trying [to score]. Now we have to get fourth [spot in LaLiga Santander] and win the Copa del Rey."