Philippe Coutinho joined the club for an initial £106m from the Reds.
It's not clear if the record signing will take part in the game.
It's a must-win game for Xavi's team. Barcelona will not reach the knockout stage of the European competition for the first time in a decade if they lose to Benfica in Lisbon.
Philippe Coutinho is not certain to play against his former club, having made a gradual slide from the third-most expensive player in history to a largely overlooked afterthought.
What has happened?
Who doesn't want to play in the European League?
The dream turned into a nightmare.
The arrival of Philippe Coutinho in January of last year was the result of two key departures - the departure of Neymar to Paris St-Germain in August of last year and the departure of Andres Iniesta to Sevilla in June of last year.
With a weak bargaining position, Barcelona never hid the fact that they were going to sign the new Iniesta and the new Neymar.
The initial fee was enough to allow Coutinho to complete his "dream" move to the Catalan coast.
The dream became a nightmare. It was obvious that he wasn't suited to either of the roles he was supposed to be in. He wanted to play further forward than Iniesta did and more centrally than Neymar did.
Instead, he preferred to roam the central areas and find space between the lines of the defence and the opposition. Lionel Messi was the main creator of the team and there was no way that Coutinho would replace him.
The social media community dubbed him 'Shootinho' because he disrupted the team's rhythm by taking too many touches and reduced to hopeful long-range strikes with sporadic success.
Loaned out and injured.
Between 2016 and the present day, Coutinho has scored 26 goals in 103 appearances for Barcelona.
The arrival ofAntoine Griezmann in July of this year made it harder for Philippe Coutinho to become a key player for Barcelona and he was sent out on a season-long loan to Bayern Munich.
In Germany, Coutinho was a bit-part player, starting less than half of the games. He scored twice off the bench against his parent club in the quarter-finals of the European competition.
In the summer of 2020, the Brazilian was sent back to Barcelona after the German club refused to sign him permanently.
The club was in a state of disarray. Messi was at odds with the club's president Josep Maria Bartomeu who was going to be forced to resign, Luis Suarez was at odds with the new manager Ronald Koeman, and veterans were being forced out.
After a promising start to the 2020-21 season, which saw him become a regular in the starting line-up, he suffered a knee injury that ruled him out for eight months, which was a blow to Barcelona's hopes of selling him.
Another wasted season was the outcome.
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The team stumbled from one crisis to another, and when Coutinho returned, Ronald Koeman was in his last days in charge. During Sergi Barjuan's final game as interim boss, Coutinho caused controversy by warming up with miserable reluctance.
If the 29-year-old thought Xavi's arrival would herald a new opportunity, those hopes were dashed.
The new boss' first game was a home win over Espanyol. The tie with Benfica was crucial to the club's hopes of retaining the title, but Xavi preferred to use three teenagers instead of him.
He did score a late penalty off the bench against Villarreal, but Saturday's home loss against Real Betis was another disappointment. After making a decent early impression, he faded badly and was replaced before the hour mark.
Domagoj explained that even though Messi has left, Coutinho is unlikely to enjoy a revival.
width and verticality are more relevant now than in the past. Xavi likes aggressive players who make runs beyond the opposition's line and attack space with pace and power. It's not possible for Coutinho to do that.
Unless the system is catered towards him, we're never going to see the full potential of Coutinho. He doesn't fit the roles of the winger or theMidfielder and the number 10 role he loves doesn't exist in such a way to accommodate his skill set.
Barcelona's greatest hope for selling Coutinho is to reduce the club's debt and possibly even fund new signings such as Manchester City's Ferran Torres, who is a main target for Xavi.
In the immediate future, Wednesday's decisive date with Bayern is another game that could well pass Coutinho by.