Laurent Blanc's side have stumbled in Ligue 1 in recent matches and have fallen behind in the title race, but continue to flourish in cup competitions.
Victory in the Coupe de France over Montpellier put them into the last 16, while they cruised into the quarter-finals of the Coupe de la Ligue with a 3-1 win over Ajaccio last month.
Holders PSG had to come from a goal down in that match, though, and can ill-afford to do the same against Saint-Etienne.
Christophe Galtier's side are unbeaten in their last 13 domestic matches and go into the PSG clash on the back of four wins in a row.
Both teams have had success in this competition in recent seasons, with PSG winning last year after Saint-Etienne lifted the trophy 12 months earlier.
PSG's latest loss came at the hands of Bastia on Saturday and the Corsicans are also in Coupe de la Ligue action this week when they welcome Rennes to the Stade Armand Cesari.
Bastia are looking to get past the last eight for the first time since 1994-95 – when they finished as runners-up – and will hope their upturn in form can help end that wait.
Having beaten Caen to reach this stage after extra time, Bastia are full of confidence and coach Ghislain Printant is upbeat about extending the side's unbeaten run to six games in all competitions.
"We will enjoy the chance to play in another competition," he said after the PSG win. "We remobilise to try and make the semi-final of the league cup.
"I am amazed by the work of my players. This result [against PSG] should make us aware that we are capable of this kind of result."
Bastia have already beaten Rennes this season – a 2-0 win in Ligue 1 last month – and the visitors will target an improved performance to keep their hopes of reaching a second final in three seasons alive.
Monaco host Guingamp at the Stade Louis II on Wednesday, while Nantes visit Lille.
After a slow start to the season under Leonardo Jardim, Monaco have reached the knockout stages of the UEFA Champions League and have closed in on the top four in the league after four successive wins.
Last season's Coupe de France winners Guingamp should not be taken lightly, though, with an unbeaten run that stretches back to the start of December in all competitions.
