Matchday four of the Champions League beckons, with plenty of sides in desperate need of points to keep their dreams alive.
Here is our take on three of the key talking points that will be debated amid the 16 games that will illuminate the European football landscape over the coming days.
Arsenal dare not lose again
It is curious to suggest Arsenal are standing on the brink of an almighty fall after their promising start to the Premier League season, but their proud Champions League record is very much on the line in Dortmund on Tuesday night.
Boss Arsene Wenger regularly comments on his side's success in navigating a path through to the knock-out stages of Europe's elite competition, but that target may look elusive this season if Dortmund follow up their 2-1 win at Emirates Stadium last month with another victory over Arsenal on home soil.
While this tie is not quite make or break for the Gunners, Wenger accepts his side travel to Germany fully aware that they dare not lose against Jurgen Klopp's impressively efficient Dortmund side.
"Is it a game we must not lose? I don't know, but anything but a win for us in Germany will leave us needing to get a positive result in Naples in the next match," accepts Wenger. "This group was always going to be tight as there is a lot of quality in there and whatever happens, our game in Napoli will be very important."
The key stats:
* Dortmund are chasing their eighth straight home victory in the Champions League and have never lost to an English side on home soil.
* Arsenal have avoided defeat in their last four games in Germany and have qualified for the last 16 of the Champions League for the last ten seasons.
* Since the second group stage was abolished in 2003, Arsenal have always reached the knock-out stages, finishing top of the group in six of the last nine seasons.
Questions over Messi?
Lionel Messi has rarely faced any form of criticism in the last few years, but there are some questions for Barcelona's Argentine maestro to answer as he prepares to return to Champions League action against AC Milan on Wednesday night.
Doubts over Messi's fitness and form have been expressed by a host of observers in recent weeks, with Neymar outshining his celebrity team-mate in his first few weeks as a Barcelona player.
As tends to be the case with Messi's performances, his each and every expression is analysed and dissected, but Barcelona boss Tata Martino has no doubts about his No. 10 ahead of the re-match against AC Milan at the Nou Camp.
"I don't think he's worried," Martino stressed when quizzed about Messi's form. "In the same way it was strange to see him score in 19 consecutive games [last season] it's also strange he hasn't scored in three games, but the only reason the question comes is because it is Messi."
The key stats:
* Barcelona are two points clear at the top of Group H, but they cannot qualify for the knock-out phase until matchday five at the earliest.
* Barca and Milan have played each other 18 times in European competitions, with the Spaniards winning seven times and the Italian's claiming five victories.
* Milan have lost 14 of the 24 games they have played away from home against Spanish opponents.
Mourinho will expect a response
Just when it seemed as if the Jose Mourinho effect was starting to fire Chelsea's burners, his side turned in a muted performance in their defeat at Newcastle on Saturday and now he will demand a response from their shock defeat in their return match with Schalke at Stamford Bridge.
Mourinho's threat to his players that the Europa League would beckon for them once more unless they clicked into gear was a clever use of mind games to inspire his own troops and if they get another win against Schalke at Stamford Bridge on Wednesday evening, their progress to the last 16 will edge ever closer.
"We have found a way to correct what happened against Basel, but I am reminding the players before every group game that there is no room for mistake, no room for more slip-ups," states Mourinho. "Yes we can focus on winning our group again, but one bad result changes everything. It is a delicate position."
Schalke followed up their humbling on home soil against Chelsea on Champions League matchday three with another reserved performance in front of their home fans against Borrusia Dortmund, but they will have been buoyed by Saturday's away win at Hertha Berlin.
The key stats:
* Chelsea have won five and drawn one of their six Stamford Bridge meetings with German opponents in European competitions.
* The Blues have finished as winners of their group in seven of their last 10 campaigns and qualified for the knockout rounds as runners-up in two of the other years.
* Schalke have lost just one of their last 12 away fixtures in European competition.
The stats zone
* FC Basel's Marcelo Diaz has covered more ground in the first three Champions League matches than any other player in the competition (40,014 metres).
* Real Madrid's Cristiano Ronaldo leads the scoring charts with seven goals to his credit so far. Paris Saint-Germain's Zlatan Ibrahimovic is on his tail with five goals, four of those coming against Anderlecht on matchday three.
* Zenit St Petersburg's Hulk has had the most attempts on target in this season's Champions League (14).
* Paris Saint-Germain's Thiago Motta has completed the most passes in the competition so far (350), with a 90 percent success rate in his passing.
* Celtic striker Georgios Samaras has committed the most number of fouls in the Champions League (14).
* Cristiano Ronaldo needs just one more goal to equal the group stage goals record of eight, jointly held by Ruud van Nistelrooy, Filippo Inzaghi and Hernan Crespo.