Barcelona made it three games without a victory on Thursday as a goalless draw with Cadiz further weakened Ronald Koeman's position as coach.

Frenkie de Jong was sent off in the 65th minute at the Ramon de Carranza stadium but holding on for a draw will earn little credit for Koeman, who was also shown a red card in injury time.

Whether Koeman is still in the post for Barca's game at home to Levante on Sunday remains to be seen but it appears now to be more a matter of when the club can find a replacement than if he will continue in charge.

"You have to always try to win each game, but you have to be realistic, you have to see the squad we have, the people we're missing," said Koeman.

Barcelona are already seven points behind La Liga's early leaders Real Madrid, albeit having played a game fewer, to go with a poor start in the Champions League after last week's 3-0 opening defeat by Bayern Munich.

A 1-1 draw with Granada on Monday did little to boost morale, with Koeman coming in for heavy criticism after finishing the game with central defenders Gerard Pique and Ronald Araujo up front.

Disappointment with the team's style and doubts around his future prompted a defiant reaction from Koeman in a press conference on Wednesday. 

He refused to answer questions, instead reading out a statement that asked for patience and insisted the process of rebuilding the team "deserved unconditional support."

That was taken as a clear message to club president Joan Laporta, who was reluctant to be drawn on Koeman's future before the match against Cadiz.

Laporta told reporters nothing would be decided on the basis of the result alone, while admitting "if we have to take decisions at a certain time, we will take them." After the match, Koeman said: "He was in the hotel and we said hello before the match. I'm sure there will be more days to talk if the club wants to talk."