How the sides shape up ahead of this week's games:
Tuesday
Celtic v AC Milan Venue: Celtic Park Kick-off: 7.45pm On TV: Setanta Ireland, Sky Sports 2
Celtic look like champions elect after their 2-1 victory at Aberdeen on Saturday sees them returning to Champions League duty with a 19-point lead in the Scottish Premier League.
Shunsuke Nakamura set up striker Craig Beattie to slot home the opener before adding the second with a superb free-kick.
AC Milan, on the other hand, languish 30 points off leaders Inter in Serie A - eight of those points were deducted after match-fixing allegations.
The acquisition of Brazilian striker Ronaldo has lifted spirits at the Italian club - he scored twice as Milan won 4-3 away to Siena on Saturday - but he is cup-tied for this clash and striker Filippo Inzagi is also side-lined with a muscle strain.
Lille OSC v Manchester Utd Venue: Stadium Lille Metropole Kick-off: 7.45pm On TV: RTÉ 2, UTV
Lille beat Manchester United 1-0 at this venue last season before finishing in the Uefa Cup spot as Manchester United were dumped out of Europe at the group stages.
Things are not going well on the domestic front for the northern French side as they lie 18 points behind leaders Lyon after their 2-1 loss at home to the reigning Ligue 1 champions on Friday night.
Manager Claude Puel may be without top scorer Mathieu Bodner as the midfielder struggles with injury.
Lille lost just one game, away to AEK Athens, on their way to qualifying from Group H.
A 2-0 win away to AC Milan, who had already qualified, assured the French club a first appearance in the knockout stages of the Champions League.
PSV Eindhoven v Arsenal Venue: Philips Stadion Kick-off: 7.45pm On TV: ITV 4
Reigning Dutch champions PSV Eindhoven got their season back on the rails with a 2-0 win at Heracles Almelo on Saturday that ensured they retain leadership of the Eredivisie as they prepare to take on last season's Champions League finalists.
A run of only one point from their previous three games had put questions marks over whether Ronald Keoman's side could retain their title.
Jefferson Farfan broke the deadlock at Heracles after 74 minutes and substitute Diego Tardelli added another in stoppage-time.
PSV managed just one point in their two Group C games against Liverpool before Christmas and didn't manage a goal against the Premiership opposition.
Real Madrid v Bayern Munich Venue: Bernabeu Kick-off: 7.45pm On TV: Sky Sports Xtra
Real Madrid's poor home form in La Liga continued on Saturday with a scoreless draw against Real Betis. Frustrations got the worst of David Beckham as the former England captain was shown a straight red card after a lunging challenge on an opponent.
The pressure mounts on manager Fabio Cappello but he can take consolation from the fact the things are not much better at Bayern, who brought Ottmar Hitzfield in as manager last month after the sacking of Felix Magath.
They have picked up just four points from their five Bundesliga matches so far in 2007.
The most recent of which was Saturday's 1-0 defeat to Alemannia Aachen which left the team 12 points behind leaders Schalke 04.
Wednesday
AS Roma v Olympique Lyon Venue: Stadio Olimpico Kick-off: 7.45pm On TV: Sky Sports Xtra (interactive)
AS Roma's faltering Serie A challenge received a heavy blow when they went down 1-0 at Empoli on Saturday. They are safe in second place, but trail Inter Milan by 14 points and show no sign of stringing together the run of wins that would be necessary to put the leaders under pressure.
They do, however, have Francesco Totti in fine form following his decision to retire from international soccer.
Fred and Sebastien Squillaci scored to earn runaway Ligue 1 leaders Lyon a 2-1 victory at Lille on Friday night.
With the domestic title all but wrapped manager Gerard Houllier will hope Milan Baros can make the same impression in the Champions League as the Czech striker did with Liverpool in 2005.
FC Porto v Chelsea Venue: Estadio do Dragao Kick-off: 7.45pm On TV: Setanta Ireland, Sky Sports Xtra
Porto maintained their lead in the Portuguese league with a 4-0 win at home to Naval on Friday, with Argentinian striker Lisandro Lopez scoring twice.
They have, however, lost two league matches so far this year and are without the very promising Brazilian midfielder Anderson, who is out with a fractured leg.
Chelsea will be aware that Helder Postiga is Porto's danger man and the former Tottenham striker will not be bothered by physical nature of the Premiership champions' defence.
Porto qualified from Group G along with Arsenal but managed just one point from their two games against Arsene Wenger's side. A return for Jose Mourinho to his former club should not concern the Chelsea manager too much.
Barcelona v Liverpool Venue: Camp Nou Kick-off: 7.45pm On TV: RTÉ 2, Sky Sports 1
If Liverpool feel their preparations for the knockout stages were bad, they can take some consolation in Barcelona's being not much better.
Rumours of a rift between coach Frank Rijaard and Samuel Eto'o persist. The Cameroon striker was left at home to work on his fitness as the team travelled for an ill-fated trip to Valencia yesterday. Such stories, of course, have been denied by both parties.
Barcelona went down 2-1 on the east coast and had Deco sent off for a studs-up challenge. Ronaldinho scored the consolation with his 16th goal of the season
Sevilla are now level on points, but with inferior goal difference, with Barcelona at the top of La Liga following their defeat of Atletico Madrid last night.
Inter Milan v Valencia Venue: San Siro Kick-off: 7.45pm On TV: Sky Sports Xtra (interactive)
Inter Milan extended their record-breaking run of Serie A wins to 16 with a 1-0 victory against Cagliari at the San Siro on Saturday.
Defender Nicolas Burdisso headed the winner from Zlatan Ibrahimovic's cross in the 11th minute to tighten his team's grip on the title race.
Valencia put themselves firmly in the title race with a 2-1 home win over leaders Barcelona in the Primera Liga last night.
Two quick goals early in the second half from Miguel Angel Angulo and David Silva settled a hotly contested match, which saw a player from each side sent off.
The result saw Valencia climb to third on 42 points above Real Madrid due to their superior goal difference.
