What to watch for in this year's UEFA Champions League

Grab your supporters' scarves and cue the ubiquitous music. The UEFA Champions League is back.

With play opening Tuesday, here is a brief primer.

Leicester City's European debut

Last year's surprise English champions will bring a familiar core to their Champs League debut.

Top scorer Jamie Vardy spurned second-place Arsenal to stay at the club, while midfielders Riyad Mahrez and Danny Drinkwater also re-upped with the Foxes.

Claudio Ranieri's side will face Porto, Club Brugge and Copenhagen in the group stages. While their opponents are largely unheralded, the added challenge of juggling domestic and Champions League schedules will be an early test for Leicester City. Goalkeeper Kasper Schmeichel will need a strong follow-up to his 2015-16 campaign if the team hopes to last in the competition.

Plus, surprising people with improbable runs is something of a specialty with this team.

Transfer drama

Soccer's transfer window is a nerve-wracking time for players and fans alike. Though to be fair, finding out if you'll need to move to a different country and learn a new language is more stressful than worrying if your new Adidas jersey is suddenly outdated.

Here are a few big transfers that have happened so far.

• Paris Saint Germain will have to get used to life without Zlatan Ibrahimovic, as the mercurial striker moved to a rebuilding Manchester United.
• New Manchester City boss Pep Guardiola brought in former Barcelona keeper Claudio Bravo, signaling the end of Joe Hart's time at the Etihad. The English netminder has since moved on to Italian club Torino. As for Bravo and Guardiola, they will see plenty of familiar faces in the group stage as they were drawn with Barça.​
• Gonzalo Higuain's record-setting transfer to Juventus should bolster its attack, but will it be enough to compensate for the departed Paul Pogba and Alvaro Morata? At least the 2014-15 finalists still have Gigi Buffon.

Higher stakes in Europa League

Don't worry Man U fans, you haven't been overlooked.

True, the Red Devils didn't qualify for the Champions League, but their journey back makes this year's Europa League more intriguing.

As of last year, the winner of the Europa League gets an automatic berth. Sevilla, who won last year to cap off an impressive three-peat, were drawn with Juve in Group H.

Will the additions of Ibrahimovic, Pogba and manager extraordinaire Jose Mourinho be enough to resurrect United? Should be fun to watch either way.

Which matchups should you watch?

Watching every single match may interfere with less important things like work obligations and social appearances. So here are the groups to keep an eye on.

Group of death: Group D (Bayern Munich, Atlético Madrid, PSV Eindhoven and FC Rostov

Not all groups are drawn equal, and Group D looks particularly menacing this year.

Bayern and Atléti are successful both domestically and in Europe, while Dutch champs PSV will be hungry for revenge against the "other" Madrid.

Rostov, who finished second in the Russian league last year, should make things difficult when the other three teams travel down the Don River.

Underrated but not overlooked: Group H (Juventus, Sevilla, Lyon, Dinamo Zagreb)

Juventus will dominate the headlines, but Sevilla is gaining ground in Spain and plays good team soccer. Lyon's recent run in France as well as Dinamo's growing confidence should make Group H one to keep an eye on.

Most entertaining: Group C (Barcelona, Manchester City, Borussia Mönchengladbach and Celtic FC)

In addition to the familiarity between Barcelona and City, this group offers a look at the lethal trident of Lionel Messi, Luis Suárez and recent Olympic hero Neymar.

Mönchengladbach and Celtic are hardly pushovers, so get ready for a closely contested group.