SEVILLE: Barcelona coach Ronald Koeman justified resting key players including Lionel Messi in Sunday's 3-2 win at Real Betis in La Liga by saying he wanted to keep his side fresh for the upcoming Copa del Rey semi-final clash at Sevilla.

The Dutchman left usual starters Messi, Frenkie de Jong and Pedri out of his starting lineup, but called on the trio to turn the game around after Borja Iglesias had given Betis a first-half lead.

Messi equalised within two minutes of coming off the bench and played a part in Barca's second goal, while Francisco Trincao thumped in the winner in the 87th minute.

"Above all I made the rotations because the players are exhausted," Koeman told reporters.

"We've played 11 games this year, 10 of which have been away from home and late at night. We are into the Copa del Rey semi-finals and Sevilla are a good side so we have to protect players to ensure we don't get more injuries."

Although the Copa del Rey ranks well below the La Liga title and Champions League in importance to supporters, Koeman is prioritising the competition this season as his side lag behind Atletico Madrid in the title race.

"It's the quickest route to win something which is very important for us. But Barca must have a winning mentality in every game and in every competition," Koeman added.

The Dutchman also revealed he had agreed to leave Messi out of the starting 11, on the understanding he would introduced the talismanic Argentine if the team were in trouble.

"I discussed resting Leo with him yesterday and we agreed we would bring him on if we needed him. He came on and changed the game, he brought life to our play," he said.

"Barca are a much better side with Messi, he is so effective and he has spent so many years proving he is a vital player to this team."

Messi, 33, had only previously begun one league game on the bench this season. He started November's home game against Betis as a substitute but came on at halftime to help turn a 1-1 draw into a 5-2 victory.