The Blues activated the striker's £7 million buy-out clause on Wednesday and look set to confirm his signing, although Alan Pardew claims the deal has been completed
Earlier on Wednesday, the European champions submitted a £7 million bid to Newcastle which triggered the release clause in the Senegal international's contract.
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With Daniel Sturridge having already signed for Liverpool, Benitez has Fernando Torres as his only recognised first-team striker for his side's trip to St Mary's Stadium.
"I don't have any official information about the situation," said Benitez.
"The club is working [to sign a striker] and we know that."
Asked whether Chelsea can sign Ba before Saturday, Benitez replied: "If we can do the business, I hope so."Newcastle boss Alan Pardew admitted he is disappointed to potentially lose such an important player, but he is pleased the saga looks to be coming to a conclusion.
Speaking to Sky Sports, he said: "Well there's no swift resolution, it's done, he'll go to Chelsea and with our blessing.
“He's been fantastic for us, it's a good club and good luck to him. For us, it's not a bad thing, for all the uncertainty, it's now done, and we'll move on. In some respects I'm pleased."