Atletico Madrid crashed out in the round of 16 last season, when they were eliminated by eventual winners Chelsea.
They have not gone beyond the quarter-final stage in the last four campaigns but will fancy their chances this year after making some significant additions over the summer.
Matheus Cunha, Rodrigo De Paul and surprise deadline day arrival Antoine Griezmann have all joined LaLiga champions Atleti — giving Diego Simeone one of the strongest squads in Europe.
Liverpool reached back-to-back Champions League finals in 2018 and 2019 but have not progressed beyond the quarter-finals since.
The six-time winners have bolstered their defensive options with the signing of Ibrahima Konate from RB Leipzig.
They will be hoping to see the real version of Thiago this term too, following an injury-hit 2020-21 campaign.
Porto made it all the way to the final eight last season, shocking the world with a stunning win over Juventus in the round of 16.
They have added Gremio winger Pepe and Bayer Leverkusen left-back Wendell to their squad in the off-season, and will relish their underdog status once again.
AC Milan are back in the Champions League for the first time since 2013-14. The Rossoneri have made some shrewd signings in the transfer market — adding the likes of Fikayo Tomori, Mike Maignan, Yacine Adli, Olivier Giroud, Alessandro Florenzi and Pietro Pellegri.
They are currently only one of five teams with a 100% record in Serie A, showing that last season’s impressive performance was not just a flash in the pan.
Champions League Group B fixtures
Check back throughout the group stage for the latest results and match reports
Wednesday September 15
Tuesday September 28
Tuesday October 19
Wednesday November 3
AC Milan vs Porto
Liverpool vs Atletico Madrid
Wednesday November 24
Atletico Madrid vs AC Milan
Liverpool vs Porto
Tuesday December 7
Porto vs Atletico Madrid
AC Milan vs Liverpool
Key fixture: Liverpool vs Atletico Madrid
This tie could well decide who claims top spot in Group B.
Progression is the ultimate aim but finishing in first place often provides a favourable tie in the next round and a better chance of reaching the tournament’s latter stages.
The two teams meet back-to-back on Matchday 3 and Matchday 4, and these clashes will play a significant role in how this group concludes.
Atleti knocked the Reds out in 2019-20, winning both legs of the round of 16 clash and doing the unthinkable — silencing Anfield on a European night.
A repeat of those triumphs will surely see Los Colchoneros escape the group at a canter.
One to watch: Antoine Griezmann
Barcelona never quite got to witness the real Griezmann.
The Frenchman does his best work when in a two-man attack, where he is allowed to drift.
At Camp Nou, he was part of Lionel Messi’s supporting cast and ended up being deployed in multiple roles, almost to plug gaps in the team.
Simeone knows how to get the best out of the 30-year-old and Griezmann will have a point to prove after an underwhelming two-year stint in Catalonia.
It could be the perfect storm for both club and player.
Breakout star: Harvey Elliott
Rising star Harvey Eliott spent last season on loan with Blackburn.
Heading into the summer, it was not known whether he would spend another year away from Anfield or if he would be part of the first-team squad.
But not only is he part of the group, he made it into the starting line-up.
Elliott, 18, started the second game of the campaign against Burnley and kept his place in the team for the visit of Chelsea.
He has not looked out of place alongside Mohamed Salah and Trent Alexander-Arnold on the right flank and he could be one of the surprise packages of the season for Liverpool — both domestically and in European competition.
Atletico’s depth may see them clinch top spot. Few in world football can rival the attacking options Simeone has at his disposal, with the Argentine tactician spoilt for choice in that part of the pitch.
Combine that with the fact that they are defensively one of the best sides in Europe — and have been for quite some time — and it makes it extremely difficult to look beyond the LaLiga champions.
Liverpool will expect to progress. They do not have as deep a squad as Atleti but do have plenty of Champions League experience, and this should be enough to see them through as runners-up.
Milan will be tipped to finish third but it might not be easy. Stefano Pioli is having to bed in a number of new signings while ensuring performances don’t drop.
They are also, as a group, relatively inexperienced at this level and that does matter. Porto could pip them to the Europa League spot.
All information correct as of 10am, September 6, 2021