Liverpool: How hard is it for Champions League holders to retain title?
Liverpool begin their pursuit of a third straight Champions League final when they face Napoli in Italy on Tuesday.
The European champions - and runners-up in 2018 - will hope to play 13 games in the competition between now and the final on 30 May 2020 in Istanbul, the scene of one of the greatest nights in the club's history 14 years ago.
But just how difficult is it to retain the Champions League? And is a tilt at doing so likely to come at the expense of the other holy grail at Anfield - a first league title in a generation?
How hard is it?
If it was easy, everyone would do it. Retaining the Champions League trophy has eluded even the greatest of club sides in the modern era.
Before Zinedine Zidane took Real Madrid to three straight wins in 2016, 2017 and 2018, no side had won the trophy back to back since Frank Rijkaard's goal in Vienna was enough for Arrigo Sacchi's grand AC Milan team to take the honour in 1990.
Even Pep Guardiola's Barcelona - perhaps the finest club side this century - 'only' managed to win the trophy twice in a three-year spell. In fact, Barcelona have never managed two finals in two years.
Since the European Cup began in 1956, 11 sides have made it to consecutive finals, with the first 30 years littered with dynasties.
Liverpool are already in the midst of a third different spell of straight finals, more than any other club.
Only Valencia have managed successive finals without winning either, while Real's run of five straight at the competition's birth looks safe - for a few years at least.
How do defending champions normally fare?
Since the Champions League began in 1992, only one defending champion has gone out in the group stage.
That ignominy is Chelsea's, who were out of the tournament six months after winning it in 2012.
Hindsight would suggest that Roberto di Matteo's Blues were unfortunate, as a usually safe haul of 10 points saw them eliminated on head-to-head away goals by Shakhtar Donetsk, whose two goals in defeat at Stamford Bridge proved the difference.
Scorer of those two goals? Willian - who, of course, joined Chelsea in 2013.
So it would be a mighty shock if the Reds failed to make it out of Group E where, along with Napoli, they face Red Bull Salzburg and Genk.
But don't forget they were uncomfortably close to being eliminated at the group stage last year. Needing to beat - you've guessed it - Napoli by two clear goals or 1-0 to progress. They duly won 1-0 win, helped by a brilliant late save by Alisson, to claw themselves over the line.
Once over that hurdle, much depends on the draw - but in the past 10 years, the previous season's finalists have reached the last eight on six occasions, lost in the semi-finals five times and won the trophy four times.
Does it affect league ambitions?
As if you didn't know, Liverpool haven't won the league title since 1990. They go into this first week of the Champions League with an early - but still possibly significant - five-point lead at the top of the Premier League.
Is it possible to focus on both?
Recent history suggests so. After all, if you have the best team in Europe there's a good chance you'll have the best team in your own country.
In the past 10 years, the Champions League winners have won their domestic title in the same season on five occasions. Barcelona are the real masters of the art - in each of their five Champions League-winning years they have also won La Liga.
Of course, squad management is likely to be crucial. After dispatching Newcastle on Saturday, Klopp bridled at a question which suggested he may choose to focus more on the league this year. But he did opt to start without captain Jordan Henderson and forward Roberto Firmino against the Magpies. Did he have one eye on Napoli?
"Any advice on how we could do it differently?" the German asked. "I am interested, what do we do? We don't make the difference between competitions, we never did. It's about availability, who is in which shape - that's how we make decisions if we can.
"Most of the time we couldn't make too many changes, to be honest. We always had to bring whoever could at least walk. We cannot go to Napoli and say we play with 60, 70, 80% of what we usually do. They are, unfortunately, really good. That's a proper opponent. They caused us problems already and we now have to make sure the problems will not be that big this time."
Last year's run to the final in Madrid certainly didn't affect Liverpool's performance in the league. After all, they collected 97 points and lost only once all season.
They won 10 of their 12 Premier League fixtures following European action, though were perhaps fortunate to be at Anfield for eight of those games, including all six during the group stage.
This year, the fixture computer has handed the Reds five home games after their six Champions League group matches, with next weekend's trip to Chelsea the only away day. In contrast, six of Manchester City's 12 group fixtures over the past two seasons have been followed by away games.
While they seem to have benefited on the travel front, Liverpool do have matches against Chelsea, last year's Champions League runners-up Tottenham and title rivals Manchester City immediately after European games - so it's hardly a cakewalk.