This might be Manchester City's biggest game of the season to date, but it sums up the way things have been going for his team that Pep Guardiola admits he doesn't know which City will turn up against Real Madrid.

The meeting of Europe's two heavyweight clubs is coming earlier in the competition this season after they both fluffed their lines in the new look league phase of the Champions League.

Real had to win their final three games in the league phase to secure a play-off berth, while City were heading out of that competition with 45 minutes to go against Club Brugge. Their three-goal second-half salvo edged them into the top 24 in the league, but the play-off draw has left facing a familiar foe.

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Madrid head to the Etihad on Tuesday for the first leg of a seismic tie. It is the fourth successive year the two clubs have met in the competition and on the previous three occasions the winner of the tie went on to lift the trophy.

That looks more unlikely this season with both teams going through their struggles, although it is City that having the more difficult campaign. They have won just eight of their previous 23 games and endured a difficult afternoon against League One outfit Leyton Orient in the FA Cup on Saturday.

Fitness issues have also blighted Guardiola's squad this season and the injuries and inconsistency has left the Etihad boss uncertain which version of his side will show up against Real on Tuesday.

"We’ve not been consistent. What’s defined the team over the last decade has been we are an incredible machine every three days, otherwise we cannot win six Premier Leagues in seven years or win the incredible trophies we have won," he said.

"We can lose because the opponents are good but we’ve not been consistent. Of course we can perform well tomorrow, of course we can perform well in Madrid, but before I can tell you that will happen I don’t know how we’ll react.

"But at the same time I will not deny that trust with the players that gave us the incredible decade and playing at the high standards I know we’re capable of. Of course we’re going to prepare today, talk with the team, we’re going to challenge and hopefully we can perform well."

City's struggles have been summed up by their recent results. A 6-0 win at Ipswich was followed by a collapse from 2-0 up against Paris St-Germain. City recovered from that to beat Chelsea 3-1, but then collapsed at the Emirates to lose 5-1 to Arsenal.

That has left Guardiola unsure exactly what version of City will turn up on a weekly basis and a team usually defined by their consistency is suddenly producing a mixed bag of performances. During his press conference on Monday, Guardiola mimed tossing a coin in the air to describe the uncertainty he has over how his team will play.

"We were unstable this season, when we were not in the past," he said. "We achieve what we achieve in the trebles and quadruples and you know how difficult it is to prove it. It's because we were a machine. It doesn't matter what happens, we were there.

"We can lose at the last minute and the opponents are good, in the Champions League we have many cases during these nine years I've been here, moments at Tottenham or moments in the last minute we could go through, not through. But always we come back, we come back. This season we struggled a lot.

"Of course it would be good to continue for the club, for the prestige to win this competition. I like to feel that we are week by week, month by month, we are there. Now I would feel, yeah, the team is consistent, we can do it. Now it's like, I don't know."