Predicted finish

1. Juventus
2. Barcelona
3. Sporting Lisbon
4. Olympiakos

Juventus

The Bianconeri will be expected to rebound from last season's crushing defeat to Real Madrid in the final and have been busy in the transfer market. Douglas Costa, Blaise Matuidi and Federico Bernardeschi add quality in key areas but there are question marks surrounding what they have lost. Dani Alves' departure was no huge surprise but Leonardo Bonucci's move to AC Milan was a blow and Massimiliano Allegri will have to remodel a defence that, until Real put four past them, had conceded only once in Europe last term.

Barcelona

Rarely since the turn of the millennium have Barcelona entered a season plagued by this much doubt. Neymar's departure for PSG, coupled by their 5-1 aggregate defeat to Real Madrid in the Spanish Super Cup, has left them uncertain of their place in the football landscape -- and even Gerard Pique admits he feels "inferior" to Real for the first time. Signing Paulinho and Nelson Semedo will not have done enough for their self-esteem; Ernesto Valverde badly needs another world-class attacker in his ranks if they are to improve on last season's quarterfinal and plenty will rest on the shoulders of Ousmane Dembele if, as expected, he ties up a move from Borussia Dortmund.

Olympiakos

Olympiakos were given a scare by Croatian side Rijeka in the playoffs but emerged 3-1 winners on aggregate and are back in the group stage after missing out last season. The Greek champions have a new coach this season in Besnik Hasi, an Albanian with European experience at Anderlecht and Legia Warsaw. He has signed powerful midfielder Vadis Odjidja-Ofoe from the latter, while Emmanuel Emenike adds a proven goal-scoring threat after arriving from Fenerbahce. They will have their work cut out to reach the knockout phase for the first time since 2013-14.

Sporting Lisbon

A single home victory over Legia Warsaw could not paper over a flat 2016-17 group stage from Sporting, who lost their other five games. Jorge Jesus' team thrashed Steaua Bucharest to earn a shot at improving that record this time and there are high hopes for the 22-year-old playmaker Bruno Fernandes, who has joined from Sampdoria and scored against Steaua. Argentine international winger Marcos Acuna, an arrival from Racing Club, was also on target in that tie. Can their flair help Sporting to a first knockout berth since 2009?

Game of the group

Juventus v Barcelona -- It wouldn't exactly be a "changing of the guard" if Juventus beat Barcelona: after all, they did just that in the quarterfinals last year. But the way things are looking, you wonder whether this one could get quite ugly. Might we see Juventus confirm that they're now definitively a step above Barca?

X factor

Ousmane Dembele -- The reported transfer fee, if correct, is astonishing. But more than the money, the biggest gamble for Barcelona is that they are effectively replacing Neymar with a 20-year-old who scored 10 goals last season. This could be an expensive mistake, but equally, the young Frenchman might provide the spark Barcelona badly need.