Newcastle boss Alan Pardew described Ba's move to Stamford Bridge as "done" on Wednesday night after the Blues triggered the £7million release clause in the Senegal striker's contract.
Ba's persistent knee problem could complicate transfer negotiations, however, and Chelsea interim manager Rafael Benitez has refused to speak about the 27-year-old.
However, Benitez has admitted the Blues must give Torres a break after blaming fatigue for Wednesday night's 1-0 Barclays Premier League defeat by QPR.
"Fernando is one of the players who needs to rest. Two or three players have been playing too many games in the last weeks and months," he said.
"Managing that was going well but against QPR it didn't work. Some of the players couldn't get to the level we were expecting.
"Without talking about names, if you have another striker you can play with two strikers if you need to.
"Or if you want to rest a striker then you can do that and at the moment we are a bit short."
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