Man United are back, how will Jose Mourinho fare at Real Madrid, the underdog to look out for and the major challenge facing Arsenal... SIX things to look out for as the Champions League returns

1. Manchester United's Resurgence

After a turbulent start to the season, Manchester United appear to be finding their form just in time for the Champions League group stages. Recent performances in the Premier League have seen the Red Devils climb the table, with new signings beginning to gel and Erik ten Hag instilling a sense of belief in the squad.

Their return to form comes at a crucial time, as they face a challenging group that includes European heavyweights like Bayern Munich. Can United maintain their momentum and make a deep run in Europe's elite competition?

2. Jose Mourinho's Real Madrid Return

Jose Mourinho's return to Real Madrid is one of the most talked-about moves of the season. The Portuguese manager, known for his tactical acumen and larger-than-life personality, will be tasked with steering Los Blancos back to European glory.

Real Madrid face a competitive group, and Mourinho's experience in the Champions League could be pivotal. How he manages the mix of veteran stars and emerging talents will be key to their success.

3. The Underdog to Watch: Union Berlin

Union Berlin have been making waves in the Bundesliga and now set their sights on the Champions League. As one of the underdogs in the competition, they have the potential to surprise bigger clubs with their disciplined and energetic style of play.

With a passionate fanbase and a solid tactical setup, Union Berlin could be this year's dark horse. Keep an eye on their performances, particularly against more established European sides.

4. Arsenal's Major Challenge

Arsenal's return to the Champions League comes with high expectations but also significant challenges. Mikel Arteta's side has shown promise in the Premier League, yet their lack of recent experience in Europe's top competition could be a hurdle.

The Gunners will need to navigate a tricky group stage, balancing domestic commitments with the demands of European nights. Their success will depend on Arteta's ability to manage his squad effectively and maintain consistency.

5. Napoli's Title Defense

Last season's surprise package, Napoli, are back to defend their title. Their attacking prowess and solid defense made them formidable competitors, and they'll be keen to show that last year was no fluke.

Retaining key players and adding depth to their squad, Napoli are a team that could once again go deep into the tournament.

6. PSG's Quest for Glory

Paris Saint-Germain's pursuit of Champions League glory continues with a star-studded lineup and a new coach at the helm. Despite domestic successes, European triumph has eluded them, adding pressure to deliver this time around.

With Kylian Mbappé leading the charge, PSG's offensive capabilities are undeniable. However, their defensive frailties could be their undoing in the latter stages of the competition.

As the Champions League group stages kick off, these storylines promise to provide intrigue and excitement for soccer fans worldwide.