It's odd how much excitement can be generated from a Champions League draw, which is essentially comprised of grown men and women pulling balls out of pots.

It's also completely understandable.

Draws construct the roads that clubs must embark on to reach the promised land, determine when and where supporters will use their vacation time, and create the most entertaining of storylines, pitting rivals against one another and triggering the return of players and managers to their former teams.

Thursday's draw at the Grimaldi Forum in Monaco was no different, as 32 clubs were sorted into eight groups of four, writing the prologue for what should be a fascinating group stage.

Here are five story lines to watch stemming from the Champions League group stage draw:

Barcelona's title defence begins

In what will be its 20th appearance in the group stage, Barcelona was drawn alongside Bayer Leverkusen, AS Roma, and BATE Borisov in Group E.

While that's by no means a weak quartet, the Catalan club can't have any real complaints about its path to the knockout phase of the competition.

Barcelona defeated Leverkusen 10-2 on aggregate when the two clubs met in the Round of 16 in the 2011-12 Champions League, a tie that saw Lionel Messi score a joint-record five goals in the second leg. Prior to that, in the same edition of the tournament, the Blaugrana pumped nine goals past BATE in the group stage.

Paris Saint-Germain, Real Madrid to finally meet again

One would think that two prestigious clubs like Paris Saint-Germain and Real Madrid have taken the pitch together with considerable frequency over the years.

That isn't the case.

After being drawn together in Group A, PSG and Real Madrid will face off against each other for only the fifth and sixth time in European competition. Their most notable confrontation came in the 1992-93 UEFA Cup, when the Spanish giant disposed of the French club in the quarterfinals with a 5-4 win on aggregate.

The first leg marked PSG's only competitive loss ever to Real Madrid.

Jose Mourinho returns to Porto

Well, well, well. Look who's going back to the Estadio do Dragao.

Chelsea once again received a cupcake of a group, drawn next to Porto, Dynamo Kyiv, and Maccabi Tel-Aviv in Group G.

Of course, that means Jose Mourinho will be returning to Porto, the club with which he won the 2003-04 Champions League before immediately departing for Stamford Bridge.

This won't be the first time Mourinho has visited his former club, however - he went up against Porto in the group stage of the 2004-05 edition of the competition during his first season at Chelsea.

Astana makes its historic debut

Drawing Astana - only founded in 2009 and the first club from Kazakhstan to ever qualify for the group stage of the Champions League - comes with a clear pro and a clear con.

Pro: Astana is arguably the weakest side in the competition.

Con: Astana is located nowhere near central Europe, meaning Benfica, Atletico Madrid, and Galatasaray will be forced to travel ridiculous distances to play the Kazakh club in Group C.

The journey is particularly brutal for Benfica, as Astana is located over 7,000 kilometres from Lisbon.

Benfica supporters looking for an alternative to the 77-hour drive can choose between a 10-hour flight or a 1,439-hour walk.

Bayern Munich, Arsenal to renew rivalry

A collective groan echoed through North London when Arsenal was drawn alongside Bayern Munich in Group F.

It was Bayern that eliminated Arsenal from the Champions League in both 2012-13 and 2013-14, defeating the Gunners on away goals the first time around and 3-1 on aggregate one year later.

However, both those battles took place in the Round of 16. Arsenal can take comfort in known that progressing past the group stage will mean avoiding Bayern before the quarterfinals.