The Real Madrid assistant coach has made the club's priorities clear in terms of competitions, but insists Los Blancos will still play to win in the Spanish top flight.
Priority was immediately refocused to the team's home encounter against Manchester United, despite Cristiano Ronaldo's hat trick inspired rout of the La Liga rival at the Santiago Bernabeu.
"We have shown we still want to win every league game," Karanka told reporters after the match. "However, the Champions League takes center stage now."
Ronaldo was hauled off with 20 minutes to go, preserving the Portuguese superstar's energy reserves ahead of the fixture against his former side.
"Ronaldo's fine. He works hard and has to play. He deserves it [the hat-trick]," said defender Pepe. "The team works hard every day. Today, we went all out. Every game is special, but on Wednesday we will have to keep it up."