Valverde brought down Alvaro Morata when he was through one on one and took the red card, something Oblak admitted the Uruguayan had to do.
"It's not nice to see, but he did it to stop us from scoring a goal," Oblak said after Real Madrid won the penalty shootout in Jeddah.
"It was a clear red card.
"Then it meant that we didn't have the clear chance we should have had.
"We had the match quite well controlled.
"There were moments when they had more possession, but we were dangerous on the counter attack.
"We only lacked a little to score a goal.
"In the end, it went to penalties and it's a lottery.
"They scored and we didn't.
"Now we have to lift ourselves up and march on ahead."