|Ronaldo will be desperate to reach his third final after losing with United last year [AFP]
Real Madrid may be finding top form in Spain but their season will be considered a failure if they fail to get past French side Lyon at the Bernabeu in the European Champions League last 16.
With Madrid's stadium also playing host to the final in May, much of the Spanish media see a 10th European title as almost an obligation this year for a Real team which includes Kaka and Cristiano Ronaldo.
But they must break through a Lyon defence which has not conceded a goal in more than 10 hours' football if they are to keep alive their dream of playing in the final in their own stadium, after losing 1-0 in the first leg.
David Beckham will return to Old Trafford for the first time in seven years as AC Milan visit his old club Manchester United, who may be without injured Wayne Rooney, in another of this week's round-of-16 second legs.
It is 11 years since Beckham's corners led to United's last-minute winning goals against Bayern Munich to hand him his only Champions League medal, and Milan may need help from his pinpoint crosses to overturn their 3-2 deficit from the San Siro.
In-form Arsenal host two-times winners Porto and Bayern visit Fiorentina in the remaining matches, both of which featured highly-controversial refereeing decisions in the first leg.
Referees are likely to be even more under the spotlight this week after soccer's rule-makers, the International Football Association, on Saturday decided to indefinitely reject the use of goal-line technology, standing firm in the face of pressure from players, coaches and the media.
Real have scored 14 goals in winning their last three La Liga games but on Wednesday must score against a Lyon side that has kept a clean sheet in their last six matches, including the first leg last month.
The last player to score against Lyon was Paris St Germain's Mevlut Erding in the 10th minute of a Ligue 1 game on January 31.
"It will be a failure to not get past this round against opponents such as Lyon, who are good but not among Europe's big teams," midfielder Guti told the sports daily Marca.
"Wednesday's game is a final for us," added Xabi Alonso after Saturday's 3-2 win over Sevilla – when Real came from 2-0 behind – put them top of the Primera Division ahead of European champions Barcelona.
Return of the prodigal son
Beckham is expected to get a warm reception at Old Trafford in the other of Wednesday's games but he is far from certain to start, having begun several recent games on the substitutes' bench.
Milan's Brazilian coach Leonardo is still hopeful the seven-times champions can turn the game around.
|Beckham won the Champions League with Manchester United in 1999 [AFP]
"Football is giving us a great opportunity. It's extraordinary to go to Old Trafford having to win in an important way," he said.
"I don't just mean winning 2-0. I mean victory, going there to score goals and play a game against a Manchester side who have their style."
Rooney, who scored twice in the first leg, suffered a knee injury during England's 3-1 friendly win over Egypt on Wednesday.
"It's one of these bad bits of luck you get – the Wembley pitch has just killed him," said manager Alex Ferguson.
Arsenal, who have captain Cesc Fabregas out with a hamstring injury, go into Tuesday's match 2-1 down to a Porto goal which had Arsene Wenger fuming.
The Arsenal manager was incensed after Colombian striker Radamel Falcao's goal from a quickly taken indirect free kick was allowed to stand.
Four-times champions Bayern, unbeaten in 18 games in all competitions, take a 2-1 lead to Fiorentina thanks to a last-gasp Miroslav Klose goal which both coaches agreed was well offside.
Next week's fixtures see Chelsea play Inter Milan, Sevilla versus CSKA Moscow, Barca against Stuttgart and Bordeaux take on Olympiakos.