Manchester City boss Roberto Mancini says 'concentration' is the key as they look keep Cristiano Ronaldo at bay.

The Portuguese superstar returns to Manchester on Wednesday for the first time since leaving United three years ago as Real Madrid head for the Etihad Stadium.

Real are on the cusp of qualifying for the knockout phase and anything other than a City win will see Mancini's side go out in the group stage for the second successive year.

And Mancini admits that Ronaldo - who he tips to win the Ballon D'Or - is almost impossible to stop.

"How do we stop him? Maybe we'll call the police," joked the City boss.

"He's a top player and, when you come up against someone who can score one or two goals every game, it is difficult. We will need to concentrate.

"For me Ronaldo deserves to win the Ballon D'Or. He scored so many goals last year and that helped Madrid finish above Barcelona.

"But I hope he can have a bad night on Wednesday. Maybe they can leave him at home."

Mancini insists that Madrid and Ronaldo will not take City lightly, despite their struggles in Europe.

"For him it will be a big night - but it's also an important game for Madrid. They still have a chance of going through to the second stage," he said.

"Players like Ronaldo and Messi are difficult to mark. You can do good work but they are still players who can score in every game. That's why they are the best players in the world."

Mancini believes City's disappointing Champions League campaign can be traced back to the final minutes of their opening game in Madrid when, with six minutes to go, they allowed a 2-1 lead to slip as they went down 3-2.

Mancini said: "If we had come back from the Bernabeu with a good result it would probably have changed this group for us.

"When you are 2-1 up with four minutes to go, you should be very strong to close the game."

The Hoops are still on a high following their remarkable 2-1 home win over Barcelona earlier in the month and take on Benfica at the Stadium of Light on Tuesday night knowing that a victory would ensure qualification through to the knockout stages of the competition with a game remaining.

Indeed, a scoring draw would take Celtic through if Spartak Moscow fail to beat Group G leaders Barcelona in Russia.

The former Celtic defender tried to put in context what it would mean for the Scottish champions to reach the last 16 of the competition for the first time since 2007/08.

"It would be a wonderful achievement for the players and the management," said Mjallby. "Obviously we can't compete financially with the other three clubs in the group.

"So I think it speaks volumes for the players, how hungry they are and their desire to improve all the time.

"No one gave us a chance when the draw was made but we always believed in the players and maybe they did even better than we expected."

Hoops manager Neil Lennon, though, is guarding against the growing feeling that Celtic are all but assured of a place in the knockout stages.

The former Celtic skipper is aware that Benfica will be going all out to get the win they need to retain their interest in the competition.

"We have done remarkably well to be in the position we are in on the back of beating Barcelona but that's gone now," said Lennon.

"We have two huge games left in the competition and this game is very important for both teams.

"This was always going to be a pivotal game for us, regardless of the Barcelona games.

"You are never relaxed whoever the opposition is, particularly at this level.

"The landscape of the group can change on one night. This will be as tough as Barcelona, if not tougher.

"We might get two bites of the cherry but we would like to do it at the first time of asking. But we will have to do very well."

Pulis has yet to see his team win on the road this campaign but they held high-flying West Ham after taking the lead through Jonathan Walters in the 13th minute.

The goal came from a well-worked corner routine that saw Glenn Whelan roll the set-piece into the path of Walters' run inside the box, with the Republic of Ireland striker firing past Jussi Jaaskelainen.

Pulis revealed he had been practising the routine to catch West Ham off guard and was pleased to see it make an impact.

"We have worked on it for the past three days," he said. "We tried it five or six times and Jonathan Walters has never scored from it so I'm glad he saved it for today.

"I spend a lot of time watching videos and watching teams and I felt if we could do this it would come off. You work on it millions and millions of times - it is lovely when it comes off."

Pulis has not seen his side win away in the Premier League since a 2-1 victory over Blackburn on January 2 but was pleased with his players' application.

"First half I thought we played well and created the better opportunities and really we needed that second goal. The worst thing that happened to us was half-time, that took the momentum away from us," he said.

"We started very sloppy in the second half, we invited West Ham onto us and they scored a goal and from that point onwards we need to show a lot of resilience and determination as a group not to concede a second."

West Ham boss Sam Allardyce felt his side were unlucky not to secure a victory that would have seen the Hammers move up to fifth in the table.

"I think in the end we were disappointed we didn't win it, given our second-half performance," he said. "I think that when you put that much pressure on the opposition second half you have got to try and a be a bit more ruthless in front of goal, a little bit more quality and composure needed and we probably would have won it, but at the end of the day it is another point."

Allardyce was without injured duo Yossi Benayoun and Matt Jarvis for the game but praised his players and reckons quality, rather than quantity, is the key.

"I was very pleased with the second-half performance and the fact the squad has performed very well yet again," he said.

"I think that while our numbers are not great our quality seems to be very good and our defensive unit was very good apart, from that corner."