Bayern Munich evolved into an unstoppable force during the 2019/20 campaign.

There was a negative atmosphere brewing at the Allianz Arena as recently as November 2019 when the axe was brought down on Niko Kovac after a shocking 5-1 defeat at Eintracht Frankfurt.

But from the moment Hansi Flick set foot in the technical area, the Bavarians released their potential as one of the best European sides of the millennia with an astonishing romp to the treble.

Bayern's superb 2019/20

They overthrew Borussia Dortmund to bag the Bundesliga and overcome Bayer Leverkusen to win the DFB-Pokal Final, but it was in the Champions League where they shone the brightest.

Bayern secured 'Big Ears' for the sixth time in their history with an astonishing run that included seven goals against Chelsea and Tottenham as well as an 8-2 thrashing over Barcelona.

That quarter-final result, the most remarkable of all, saw then-loanee Philippe Coutinho finish off the Lisbon rout with two strikes against the very club that had sent him packing to the Bundesliga.

Coutinho returns to Barcelona

It's fair to say the Brazilian's loan spell was bountiful by way of securing the treble, so much so, in fact, that new Barca boss Ronald Koeman ensured that he stayed at Camp Nou for 2020/21.

It's still early days, but Coutinho already looks twice the player who failed to live up to his €160-million transfer fee during his first 18 months after kissing goodbye to Liverpool.

So, what changed? Well, aside from soaking up the confidence and class of Bayern during his year there, it's clear that the physical regime being undertaken in Bavaria rubbed off on Coutinho too.

Coutinho's body transformation

You've probably seen images over the last few months showing the crazy body transformations executed by players like Robert Lewandowski and Leon Goretzka while training with Bayern.

It's clear that the club has a strategy to bulk up their players and it only took one season for that to envelope Coutinho with images showing how his physique has changed before and after his Bayern loan.

Check out some of the photographs down below to see Coutinho's new, muscular frame and also some training footage from Instagram that gives us a potential glimpse into his new routine.

Confirmed increase in muscle mass

Is it just the photography? Is it just the trick of the light?

Well, no, because Brazil manager Tite told Spanish newspaper Marca that Coutinho had indeed put on muscle weight during his year away from Barcelona.

"There's a factor you have to bear in mind; Coutinho is a player who is very dedicated to the physical aspect," he explained in October. 

"This is even more so after his spell at Bayern Munich, where he gained five kilograms in body weight, four kilos (9lbs) of which were muscle mass. He's improved a lot physically."

Now, naturally, it takes more than a few bicep curls to elevate yourself from a Barca flop to one of the club's finest players, but surely Bayern's physical work with Coutinho has contributed to it.

Besides, there's clearly some worth in packing the squad in the gym when you consider how dominant Bayern were last season and perhaps a few clubs could take a leaf out of their book.

Barca fans will just have to keep their fingers crossed that Coutinho doesn't revert back to his skinnier frame within a few months of being back in Catalonia.