El Grana secured a much-needed win through Yacine Brahimi's early strike, but also had goalkeeper Orestis Karnezis to thank after the Greece international pulled off a series of saves to thwart the Catalans.
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"Football can be unfair," the 52-year-old told Sport.es.
"We accept it when it comes up heads and get on with things when it comes up tails.
"The league is the sum of all parts and our chances to win are becoming less. We'll see how the day ends - we have done everything to win but we are not there.
"Football is made up of little moments. We kicked from the start and we have done everything to win but score. Football is unpredictable."
The loss to Granada completed a disappointing week for the Catalans after being knocked out of the Champions League by Atletico Madrid on Wednesday, but Zubizarreta was quick to change focus to this week's Copa del Rey final against Real Madrid.
"When you get knocked out of a competition like the Champions League it's not the best news," the former goalkeeper continued.
"That's why this game [against Granada] was important to regain confidence. We have done that but not got the result. Now we have cleanse our minds ahead of Wednesday's game."
Barca face Madrid in Valencia's Mestalla on Wednesday, looking to seal their 27th Copa del Rey.