Lionel Messi cut a dejected figure in the Spanish capital as he left the pitch in Madrid last Saturday - Barcelona's immaculate undefeated streak had come to an end as arch rivals Real Madrid edged a tense El Clasico 2-1 to go temporarily top of the table.
Despite Blaugrana halving the deficit in the second half through Oscar Mingueza, the Argentine was unable to inspire a late comeback for his side, who suffered their first league defeat in 19 games.
Sitting just two points below Atletico and one behind Real, Blaugrana are far from out of the enthralling title race that has recently emerged in Spanish football, and their next league fixture against Getafe will be pivotal in righting the wrongs of the defeat in Madrid.
Before the Argentine and Barcelona focus on what is set to be a tense finish to the La Liga season however, their interest will be occupied elsewhere as they prepare for a monumental Copa del Rey final with Athletic Bilbao this weekend - an opponent Messi knows all too well.
With more than 40 goals and assists against Los Leones in all competitions, Messi's sheer brilliance against them in previous fixtures is undeniable, yet his most recent cup clash with Bilbao earlier this season proved to be somewhat of an anomaly in this narrative.
Visibly demonstrating his frustrations at Barcelona's 3-2 defeat in extra-time, he received a first Barcelona red card in his 753-match club career for sensationally lashing out at Asier Villalibre moments before the final whistle - as Blaugrana crashed out of the Spanish Super Cup.
Should lightning strike twice for Messi in Seville on Saturday, it is likely to leave a sour taste in the mouth of the Argentine and subsequently cast even more doubt on his future - as he continues to ponder the prospect of seeking pastures new.
With the fate of the league title hanging in the balance and disheartening defeats in domestic and European trophies looming over wary Catalonian heads, a win for Barcelona could make all the difference in them kickstarting an emphatic league and cup double or ruing a second successive trophyless trauma.
Tip of the Fixture
Blaugrana edged past Bilbao 3-2 in the previous meeting between the two, and it's difficult to see there being much in this one either.
Despite - what has been in stages - an underwhelming season for the Camp Nou outfit, Messi looks set for another successful season individually, with 29 goals and 13 assists to his name, and he'll be determined to emulate this success for his club.
(Odds correct at time of writing, subject to change).
This is far from Messi's first Copa del Rey final against Athletic Bilbao - the Argentine has faced off against Los Leones in three finals previously and he has a 100% record in these circumstances, winning 4-1 in 2008/09, 3-0 in 2011/12 and 1-3 in 2014/15.
In addition, he has played Athletic the fourth-most of any side in his club career (40) - and he has an exceptional background of 27 wins, nine draws and just four losses against the Basque outfit.
Additionally, the prolific forward has returned dozens of goals and assists against the side, his unmatched tally of 27 goals and 11 assists in just 35 games means he has averaged more than one goal contribution in every game he's played. Astounding.
Barcelona have only lost once against Bilbao when Messi has scored - in a first leg fixture of 2015/16 Copa del Rey quarter-finals, avoiding defeat in the other 19.
Messi's red card in the Spanish Super Cup final against Marcelino Garcia Toral's men was the first of his Barcelona career, seeing him being dismissed after 753 appearances without receiving his marching orders.
Although the number 10 has never scored a hat trick of goals against Los Leones, he has scored a trio of assists in a 5-2 away drubbing in the 2014/15 La Liga season.
In the cup competition, Messi has recorded six goals and three assists against Los Leones, averaging a goal contribution every game against them.
Atletico Bilbao 1-3 Barcelona
Copa del Rey Final
May 30, 2015
Bringing yet another piece of silverware back to Catalonia, a mercurial Messi struck twice in a convincing Barcelona win - including a genius goal for the game's first.
Receiving the ball on the halfway line, Messi unbelievably dribbled through three Bilbao players, evading a fourth as he ran into the box to finish emphatically.
The goal is widely regarded as one of the greatest goals Messi has ever scored and that Spanish football has ever seen, and is still discussed and dissected to this day.
After Neymar doubled the lead before the break, the Argentine bagged the third in the second half, converting an exquisite Dani Alves cross from close range.
Despite a late consolation from Inaki Williams, the tie was already settled as Luis Enrique's side were crowned champions of the cup once again.
Athletic Bilbao 1-4 Barcelona
Copa del Rey final
May 13, 2009
Pitching in with a goal and an assist, a young Messi helped Barcelona fight back from a goal down to win their first Copa del Rey in 11 years.
Pep Guardiola's side went behind within eight minutes before Yaya Toure's equaliser on the half-hour mark was followed by a flurry of second-half goals.
Kickstarting the comeback, Messi was on hand to put Barca ahead in the fixture, firing a low shot past Gorka Iraizoz after a scramble in the 18-yard box.
Just two minutes later and he had architected the third, playing through Bojan with a defence-splitting pass, who finished with ease.
Xavi rounded off proceedings with a stunning free kick, in one of many successful occasions under the Guardiola regime.
Athletic Bilbao 2-5 Barcelona
February 8, 2015
Messi played a huge part in this La Liga fixture - recording one goal and three assists as Barcelona extended their unbeaten streak to nine and continued to breathe down the neck of league leaders, Real Madrid.
Fifteen minutes into the game, he opened proceedings when his free kick deflected off the Bilbao wall, subsequently flying into the back of the net, to give the visitors the lead.
He followed this up with assists for Luis Suarez and Neymar either side of an own goal from Oscar de Marcos who carried a shot from the Argentine past his own 'keeper.
Messi was also heavily involved in his side's fifth in what was a comprehensive victory for Barcelona and a trademark night for the number 10.
Barcelona 5-1 Athletic Bilbao
December 1, 2012
Another La Liga drubbing. Another Messi masterclass.
A brilliant brace from the Argentinian talisman took him one short of Gerd Muller's record of 85 goals in a calendar year - a record which he famously surpassed.
His 11th double of the season was pivotal as his side cruised to a 5-1 thrashing at Camp Nou.
The first was an exquisite lob, beating both the goalkeeper and his retreating defenders, who were unable to keep it out despite their best efforts.
Rounding off intricate interplay with Jordi Alba and Pedro, he cannoned the second home with his right foot to round off a remarkable performance.
Athletic Bilbao 2-3 Barcelona
January 6, 2021
Messi's other fixture against Bilbao this year went slightly more according to plan, as he carried them to a hard-fought victory in the league.
Following an early opener from Inaki Williams, Barca quickly responded - Messi's ridiculous long-range pass found its way to Frenkie de Jong, whose cross was headed home by the youngster, Pedri.
The 18-year-old turned from goalscorer to provider when he returned the favour for Messi, his audacious backheel pass provided the Argentine with an easy tap in to put the visitors ahead.
Leo added insult to injury in the second half, thumping a well-struck shot off the bar and over the line to ensure the three points for the Catalonian outfit.