De Sa's troops – on 44 points, eight behind table-topping Kaizer Chiefs – have two games in hand over their Soweto rivals.
"We are one point better than where Pirates were last year at this stage of the season," De Sa pointed out.
With two away games for Pirates, including the Cape Town assignment against an Ajax side desperate to move away from the relegation zone, many have already written off the defending champions.
"If you want to predict whatever, that's fine," he said.
"We still think we have a chance and we'll keep on doing our best until it's zero chance.
"When it's no longer mathematically possible, then it's over. Until then we will keep on trying our best."
De Sa said nothing less than a win would be required against Ajax who picked up their first win in 2013 in their previous fixture against Free State Stars.
Playing to win
"If we're going to have a chance of winning anything, we have to play every game to win. We've been trying to do that for a while, we are depleted and we know that but it's no excuse," he said.
"Going to Cape Town is no different. I don't think Pirates have a very good record of late [there] but we have to put all that behind us."
De Sa also explained the games in hand his side hold over Chiefs would be meaningless unless Pirates picked up all three points.
"We've got to go there and try and get a result. It's a game in hand, but a game in hand is worth nothing if you don't win it.
"We've got to make the best of it and it's going to be tough."
De Sa thought Ajax were a better side than their log position of third from bottom indicated.
"Ajax have never been a bad team, they were just going through a bad patch and you could see how they played against Free State Stars, they've always been an exciting football team.
"They have a lot of good youngsters and maybe they've turned the corner, who knows?"
The match in Cape Town is a catch-up game for the Buccaneers who progressed to the next round of the African Champions league over the weekend with a win over Zambian side Zanaco.
Pirates showed good depth in their squad in the encounter and De Sa said he was pleased with the fringe players in his squad who were able to do the business.
Sit and cry
"Those are Pirates players that we have available and who are ready to do the job. We can't sit and cry about the players that are injured until next season, we have to just keep going.
"There were a couple of guys who played well in Zambia and then against Zanaco back home over the weekend so I'm happy with the way they've put their hands up," he said.
"Sometimes it's what you need – for a couple of guys to be motivated and bit of new blood – and it's great."
In the other league fixture on Wednesday evening SuperSport United host Chippa United at Lucas Moripe Stadium. – Sapa