Bielsa confident in refreshed Marseille
In their first match following the mid-season break, Ligue 1 leaders Marseille travel to the Stade des Alpes looking to avoid an upset against a Grenoble side who top Group C of the French fourth tier.
Olivier Saragaglia's men top their Championnat de France Amateur pool by a point but will be huge underdogs even on home turf.
Bielsa has urged his charges to make the most of their mid-season rest and take their impressive Ligue 1 form into the cup.
"The break was necessary and the team will return refreshed," he told a news conference on Friday.
"Their state of mind and physical condition is very positive. The group is enthusiastic.
"Grenoble are a team with an excellent attack, they have youth but also plenty of positive experience. We will prepare exactly the same way for cup and league matches."
Bielsa, who has doubts over midfielder Romain Alessandrini's availability, also voiced a degree of concern over the likely state of the pitch on Sunday.
With rugby union side Grenoble due to face Oyonnax on Saturday, Bielsa acknowledged the pitch would "suffer".
"Yes there is a rugby match [on Saturday] and the pitch will suffer but it's not a serious factor," he added.
"Both teams will play on this pitch and share the same problems. It is therefore fair."