Sydney confident even without Del Piero
"Hopefully he should be all right for next week, we'll just wait and see," Farina said of Del Piero. "It's more precautionary than anything and it'll probably give him time to freshen up as well.
"It's just one of those unfortunate things. Alessandro looks after himself very well but we have to be realistic and say that we will miss him through injury for certain games during the season.
"He's 39 but still going well and he's still playing now because he looks after himself extremely well.
"We've always been reasonably confident that if we lose any player we can cover them ... with the squad we've got now I think irrespective of who's out, as long as all the others are fit we should be ok."
Farina confirmed Richard Garcia will replace Del Piero, with Despotovic, who has scored in both of his appearances off the bench since joining the club last month, to start at striker.
"Ranko will start," he said. "I've been very happy with him, he's still probably a little bit off in terms of his full fitness for 90 minutes but he's a good pro.
"He's been working really well and came in in reasonably good condition so hopefully we'll get an hour plus out of him on Saturday."
The coach also revealed Sebastian Ryall is 'more than likely' to start at left back with Ali Abbas to move forward after playing in defence last week.
The Sky Blues have risen to third spot on the ladder on the back of four straight victories and enter Saturday's clash full of confidence.
But Farina dismissed suggestions it is a good time to be playing the Mariners who are still finding their feet under new coach Phil Moss after the shock departure of Graham Arnold.
"I don't think it's ever a good time to get the champions, especially at home, and it was a horror trip for Sydney last year going up there," he said.
"I think that memory is still in a lot of the players' minds, 7-2 is not something you like but that's what can happen.
"And now they're the champions as well they've got a lot of confidence so we're going to expect a tough game."
Meanwhile, Farina says the Sky Blues are not in a position to make a play for Socceroos captain Lucas Neill.
He added: "Unfortunately we've got no spots left so we're not considering anyone at the moment, we've got a full roster and that's it, there's no room."