Among the Dutchman's many tasks is to ensure Lionel Messi stays motivated after the club's talisman sensationally tried to leave the club last month before deciding to stay for at least one more season, Reuters reported.
Most importantly, he must devise a way to get the team winning again after a first trophy-less season since 2008, which was compounded by the humiliating 8-2 loss to Bayern Munich in the Champions League.
Unpopular president Josep Maria Bartomeu clung to the memory of Koeman's free-kick strike against Sampdoria which delivered Barca's first European Cup in 1992 when he presented the Dutchman as a figure the club and fans could all rally round.
Indeed, it is no exaggeration to say Koeman's status as a crucial figure of Johan Cruyff's 'Dream Team' earned him the job as much as his patchy record as a coach.
Koeman's only real success as a manager has come in his home country, winning league titles with Ajax Amsterdam and PSV Eindhoven as well as leading the national team to the European Championships before leaving the role to join Barca.
His last major trophy came in 2008, a Copa del Rey triumph with Valencia which was one bright spot in a terrible campaign where he was then sacked with the team on the brink of the relegation zone.
Koeman had tried to pull off a clear-out of high profile players at Valencia and faces a similar task at Barca, with Bartomeu warning right before the Dutchman's appointment that long-serving players would be shown the door.
Ivan Rakitic has already left for Sevilla while Koeman has told Arturo Vidal and Luis Suarez they are no longer needed, although the club has yet to find a buyer for either player.
The coach is keen to bring in Netherlands internationals Georginio Wijnaldum and Memphis Depay while Barca has also been in discussions with Inter Milan forward Lautaro Martinez.
But the club's ability to finance new arrivals is constrained by the COVID-19 pandemic and will hinge on Barca reducing the highest wage bill in world football.
The club's financial problems and Messi's attempted move have led to increased pressure on president Bartomeu, with fans currently campaigning to force a vote of confidence against him.
Yet beyond the gloom there is also plenty of excitement about Ansu Fati, 17 who made an explosive rise from the youth academy into the first team last year and could genuinely be the heir to Messi whenever the Argentinian does choose to leave.
Barca is resting for the first two weeks of the new season, which starts on Saturday, due to participating in the Champions League and begins its campaign at home to Villarreal on September 27.