With the UEFA Champions League picture beginning to take shape, there is a certain trio of key fixtures to watch for in particular in Matchday 5's action.
Some teams have the chance to solidify seeding in the round of 16, but it will not be without a significant challenge of hostile environments, scrappy opponents and some determined to hang on in the discussion of the next set of matches.
Here is a breakdown of what to watch for as the road to Wembley Stadium in London continues.
Galatasaray AS vs. Manchester United FC
The Red Devils won Group H easily and should have a slight advantage against the Istanbul-based club on Tuesday. Galatasaray is tied for the critical, final second position out of the group, and to notch three points in this one would be a big bonus.
With such an explosive attack featuring Javier Hernandez, Robin van Persie and Wayne Rooney most prominently, the Red Devils have scored an English Premier League-best 29 goals in just 12 matches.
That should be too much firepower for the Lions to contend with, but there is one huge factor working in the home team's favor: the loudest crowd of fans in the world.
That's right. The Guinness World Records made it official in 2011, as the Turk Telekom Arena erupted for a reading of 131.76 dbA, a unit essentially designed to more accurately gauge decibels and loudness. In other words: very loud.
That may be enough to save Galatasaray in this one. The club has only scored one goal in the entire UEFA tournament. They will need far more than that to keep up with United, as they lost 1-0 in the last fixture to open Champions League play (h/t BBC).
FC Porto vs. GNK Dinamo Zagreb
The Portugese Primeira Liga club have to be considered the heavy favorites as they host this fixture against a Dinamo Zagreb team that has lost 10 matches in a row.
Vitor Pereira managed his men to the Primeira title in 2011-12, and they show no signs of letting down. According to UEFA.com, the Dragons were undefeated at home during that run, which should translate nicely to this Wednesday night showdown.
The addition of Jackson Martinez on the attack has only helped the cause, as the striker has eight goals (h/t Soccer Way) in nine appearances in his new environment.
Lucho Gonzalez and Steven DeFour notched the goals for Porto in the last meeting between these two in September, and the Dragons also kept a clean sheet in the victory (h/t 1000Goals.com).
This just seems like it will add to the Blues' grief. The Croatian Prva HNL reigning champions are simply overmatched and will look to play the ultimate spoiler role with Porto already through to the final 16.
FC Zenit St. Petersburg vs. Málaga CF
With a draw by AC Milan and a victory by FC Zenit, the defending Russian Premier League champs can knot themselves at six points a piece with the Red and Blacks.
That would cause a massive shakeup to the Group C standings and knock Anderlecht down to last, with the Russians getting a shot to take them down in the final fixture in early December.
Meanwhile, the Anchovies—who sit in fifth place in La Liga's standings—merely need a draw to wrap up the group title. So it is definitely a must-win for Zenit St. Petersburg in Wednesday evening's battle in Petrovsky Stadium.
The home team was overmatched in their trip to La Rosadela in Matchday 1, when they fell to Malaga 3-0 in a one-sided affair. It's essentially a win-or-go-home scenario, and Luciano Spalletti's club must get it done.