The Giallorossi have collected just two wins in the last two months and crashed out of the Coppa Italia with a 2-0 home defeat to Fiorentina on Tuesday.
That outcome followed Saturday’s 1-1 result against Empoli, their fourth straight league draw, that dropped Roma seven points adrift of Serie A leaders Juventus.
Lack of goalscoring has been Roma’s biggest problem, with Garcia’s men having found the back of the net just three times in their last four games.
“Only a victory can help us regain our confidence,” Garcia told the Italian press. “We are disappointed just like our fans are as we wanted to progress to the semi-finals of the Coppa.
“But must look ahead and focus on Saturday’s game. We now need to turn our attention to Serie A and the Europa League. We have to work harder in order to turn this situation around.”
“We must do better on defence and be more efficient in attack.Once we have all of our players available, we will be stronger and do better.”
New Roma signing Victor Ibarbo will not face his former club this weekend.
Ibarbo sustained a thigh problem against Fiorentina in his first appearance for Roma and the Colombian forward has been ruled out for five weeks.
Ibarbo has joined injured midfielders Kevin Strootman and Daniele De Rossi as well as striker Juan Iturbe on the sidelines.
To add to Garcia’s woes, defender Kostas Manolas and midfielder Alessandro Florenzi must serve a one-match ban on Sunday.
Cagliari have won four games this season and go into the encounter at the Sant’ Elia eager to bounce back from a 2-1 defeat at Atalanta last time out that halted their three-match unbeaten run.
The outcome left the Sardinians in 17th position, just one point and one place clear of the drop zone.
Cagliari coach Gianfranco Zola will have all of his players available, with the exception of injured playmaker Andrea Cossu.