Tata Martino won't need reminding that it was Gracia's hard-working side that were the first team in La Liga to take points from the Blaugrana earlier in the season.
Another failure in this one could derail Barca's title hopes completely.
There will certainly need to be a vast improvement in performance from their last league fixture against Real Valladolid.
It beggars belief that a team replete with all of it's star players should play so poorly against a team fighting relegation.
These "freak" results do happen occasionally, of course. But it was the manner of the defeat that has left a sour taste.
Perhaps Barca were the victims of the "FIFA virus" again? Fatigue certainly seemed to play a part in Valladolid, and a 10,000-mile round trip for Neymar would surely have taken its toll.
In any event, there simply must be an immediate improvement, because fifth-from-bottom Osasuna will provide a stern test.
Just three points above the relegation places, there is a very obvious need for the points to be taken home to Pamplona.
Only two wins in the last nine, per WhoScored.com, suggests a team woefully out of form. However, form guides can sometimes be misleading.
We only need view the way that title-chasing Atletico Madrid were torn apart in a recent 3-0 loss to Los Rojillos to understand that Osasuna will carry a goal threat, and they will be no pushovers.
Former Barca player Oriol Riera could well come back to haunt his former employers if he is not well chaperoned by Gerard Pique or Javier Mascherano.
Riera will lead the line in Gracia's usual 4-2-3-1 formation.
Are Barca out of the title race if they don't beat Osasuna?
Roberto Torres, sitting just behind, has been instrumental in much of Osasuna's attacking excellence, but he will find it difficult to impose his natural game against Sergio Busquets.
Barca's most reliable general was a little off-colour in the Valladolid fixture and will be keen to make amends.
Per WhoScored, Osasuna have had the lion's share of possession over their last five games, so Xavi Hernandez's position alongside Busquets is assured as Barcelona look to win the possession battle.
Martino's midfield conundrum is whether to choose the more incisive Andres Iniesta over a creative Cesc Fabregas.
It's likely to be his only selection dilemma in the attacking areas—the front three of Neymar, Lionel Messi and Alexis Sanchez picking themselves.
Oier and Damia are comfortably Osasuna's worst performers over the last few weeks, so full-backs Dani Alves and Jordi Alba should aim to get forward at every opportunity.
And with only half a dozen home games left, patrons might start getting a little misty-eyed when they realise that there is just 520 minutes left to witness the excellence of Barca's best-ever keeper Victor Valdes at Camp Nou.