The winners of the previous two La Liga titles have struggled in their opening five league fixtures of the new campaign.
Ernesto Valverde's side currently sit in eighth position, four points off leaders Athletic Bilbao and bitter rivals Real Madrid. Barca succumbed to their second defeat of the season at the weekend, losing 2-0 to Granada, piling the pressure on Valverde.
Their next challenge comes tonight as they host an in-form Villarreal side. Here is how they are expected to line-up.
Goalkeeper and Defenders
Marc-Andre ter Stegen (GK) - The German has solidified his place as one of the world's top goalkeepers with several fine performances over the last few weeks. Ter Stegen has, literally, saved Barcelona on multiple occasions this season and will be desperate to earn his first league clean sheet tonight.
Sergi Roberto (RB) - A lack of strength in depth in the right back position has opened the door for the Spaniard to claim a starting spot. The 27-year-old is more than capable in the position but has fallen down the pecking order recently, with Nelson Semedo becoming Valverde's preferred right back. Barcelona will hope Roberto can add to his 34 assists in what could be his 250th club appearance.
Gerard Pique (CB) - Barca's defensive issues have been epitomised by Pique's drop in form this season. The 32-year-old had one of his best campaigns to help his side to their second successive league title, but has already picked up four yellow cards in the opening five fixtures as he has failed to contain his frustration.
Clement Lenglet (CB) - With first choice centre-back Samuel Umtiti sidelined for at least another month, Lenglet will be given his chance to impress at the Nou Camp. The Frenchman has played every minute so far this season, and will hope that he can retain his starting place upon the return of his fellow countryman.
Nelson Semedo (LB) - A long-term injury to Jordi Alba, and Junior Firpo's lacklustre form could mean that Valverde may be forced to bring his first choice right back in as cover.
Frenkie de Jong (CM) - The Dutchman should be full of confidence after being named in the Best XI at last night's Best FIFA Football Awards. The 22-year-old has been one of Barca's better players this season, and will continue in the starting XI this midweek.
Sergio Busquets (CM) - Barcelona have struggled defensively and will be desperate to resolve this. In terms of defensive midfielders, they do not come much better than Busquets, and his return will be invaluable in their search for their first league clean sheet of the season.
Arthur Melo (CM) - The Brazilian has impressed so far this season, directly contributing to a goal every 55 minutes. The 23-year-old already has a goal and assist to his name during his two appearances.
Lionel Messi (RW) - Barcelona have certainly missed their talisman, but the newly crowned FIFA Player of the Year is set to make his first start of the season during this midweek. The Argentine has played just 75 minutes of the new campaign and will look to add to his 603 goals and 242 assists in his 690th appearance.
Antoine Griezmann (LW) - The Frenchman's quick start to life at his new club has stalled in recent weeks. He could be set to move out to the left due to the returns of Suarez and Messi.
Luis Suarez (ST) - The 32-year-old will undoubtedly lead the line once again as he hopes to add to his two goals so far this season. If Barcelona's defence is breached once again, they possess enough power in attack to get them out of trouble.