The Liga giants emerged as 2-1 winners courtesy of a double from Cristiano Ronaldo, but the visitors were made to work hard for the victory when Iago Aspas equalized soon after Ronaldo had broken the deadlock midway through the second half.
And in his post-match press conference, speaking instead of coach Jose Mourinho, Karanka asserted Madrid had to take its chances to ensure victory because opportunities to score were few and far between.
“The most important thing is to create chances. Last year, we had a lot, this year there are slow to come, but they will eventually come.
“The first 20 minutes saw us struggle to get into the match, we couldn’t find a way in, but in the last 15 minutes, we controlled the game a bit more.
"We were able to finish the match, but the goals didn’t come. They also had chances and slowly created goal-scoring opportunities, and in the end, they could have equalized, which would have been a shame."
The 39-year-old also commented on Celta's chances of retaining its status in the top tier of Spanish football amid the serious threat of relegation with Paco Herrera's side currently second from bottom in La Liga.
He added: "[Celta] have a lot of people in attendance and have good, quality players. It’s hard to say whether they will be among the bottom three or not, but they are working hard."