LONDON - There will be plenty of tension in the air in North London on Wednesday when out-of-sorts Arsenal face Borussia Dortmund seeking to qualify from the Champions League group stage for the 15th successive season.
There will be plenty of nerves elsewhere in Europe too as the opening phase of the competition draws to a close with Matchday Five providing the last chance for some clubs to keep alive their hopes of reaching the last 16.
Six teams have already qualified for the knockout rounds: reigning champions Real Madrid, Barcelona, Paris St Germain, Dortmund, Bayern Munich and Porto.
Others, like last season's beaten finalists Atletico Madrid, Chelsea, AS Roma, Shakhtar Donetsk, Bayer Leverkusen and FC Basel have a realistic chance of joining them with a match to spare, while for others only a dramatic improvement will see them stay in contention.
The latter include big-spending English champions Manchester City who are bottom of Group E with two points from four games but will remain in contention if they beat Bayern at home on Tuesday or CSKA Moscow versus Roma ends in a draw.
Bayern have already clinched top spot but Roma (4 points), CSKA (4) and City (2), are all tightly bunched.
Roma, who beat CSKA 5-1 in the opening match, will go through if they beat the Russians again and City lose at home to Bayern, as they did in the group phase last year when the Munich side beat them 3-1 in Manchester.
While City look for a win over familiar German opposition in the north of England, Arsenal will do the same in the capital after blowing their chance of securing a last 16 spot on Matchday Four.
Arsenal were coasting to victory over Anderlecht, leading 3-0 with half an hour to play, before allowing the Belgian side to recover and steal a point in a 3-3 draw.
However, they should still qualify in second place and will do so if they get at least a draw against Dortmund and the other game between Anderlecht and Galatasaray is also drawn.
But if Arsenal slip up again -- entirely possible as Borussia beat them 2-1 at the Emirates in the group stage last season -- and if Anderlecht or Galatasaray should win, then nothing will be decided until the final matchday on Dec. 9.
Arsenal though are not in the best of form going into Wednesday's game, and their late capitulation to Anderlecht has been followed by successive league defeats to Swansea City and Manchester United.
Some of Europe's traditionally stronger teams are, like Arsenal, also not yet certain of their survival, including five-time European champions Liverpool who are battling to stay alive in Group B.
Liverpool face Ludogorets in Bulgaria on Wednesday, and will be out if Basel beat Real Madrid and the Merseysiders fail to beat the Bulgarians.
Ludogorets, who have been far from disgraced in their first Champions League campaign with a win over Basel to their credit, will finish bottom of the group if they lose and need to beat Liverpool to have a chance of third spot.
One criticism of the Champions League in recent years has been that the same teams play each other too often in the opening phase, making the competition less exciting.
That will change from next season with a new seeding arrangement in place, but the fourth meeting between Schalke 04 and Chelsea in little over a year could prove incredibly enjoyable for the German side's new coach Roberto Di Matteo.
He led Chelsea to Champions League glory when they won the title in 2012 but was sacked six months later.
Chelsea top Group G with eight points, three points clear of Schalke, and while the Londoners are virtually certain to qualify, Di Matteo's side can make them wait until the last match and boost their chances with a win to lead the table.