?FC Barcelona coach Pep Guardiola on Monday expressed his anger at the challenge that has left him without star striker Leo Messi for between three to six weeks.

A late challenge from Atletico Madrid defender Tomas Ujfalusi at the end of Barcelona's 2-1 win in the Vicente Calderon Stadium left Messi with strained ligaments on his right ankle.

He will have tests to discover the extent of the injury, but first impressions are that he will be out of action for between 20-45 days and Guardiola is indignant at the challenge that left his player on crutches.

"The images of the challenge speak for themselves. If Atletico Madrid are as aggressive as that all season they can beat any side - even Real Madrid. If they keep that up all season they could even win the title," said the Barcelona coach in the Monday editions of the Spanish sports press.

"I don't want to say that Atletico Madrid used violence, that would be to set a bad example, but you can't go around saying that you have to stop Messi by any means possible," he said.

Guardiola's words come just a few days after Real Madrid coach Jose Mourinho said that referees had a duty to protect Cristiano Ronaldo from hard challenges. Guardiola believes that privilege should not be just reserved for the two star players.

"Referees don't have to protect Messi or Cristiano, they have to protect everyone," he said.