He joked that a change of policy will happen "when the sun falls from the sky," according to Speed Week.
Pastor Maldonado brings millions to the famous British team from his native Venezuela, and he won May's Spanish Grand Prix from pole.
But Speed Week said his carbon-crunching mistakes - the latest during a demonstration run in Caracas at the weekend - are costing Williams a substantial amount of money as well.
Brazilian Bruno Senna has also failed to shine throughout the first half of the 2012 season, while the highly regarded and Wolff-managed reserve driver Valtteri Bottas waits in the wings.
Wolff, however, said it is "too early" to say what Williams' 2013 lineup will be.
"The driver question has always been something that is very important to Frank (Williams), who has a lot of expertise," he is quoted by motorline.cc.
Wolff said it is too simplistic to say that a more experienced pair of drivers would have done a better job at the wheel of Williams' much-improved 2012 car.
And "Will Pastor or Valtteri be top drivers in the future? I believe so," he said.
"So maybe the situation at the moment fits very well with the car, even though that's something difficult to understand," said Wolff.
"We have seen the driver (Maldonado) being very good this year in Barcelona -- or was that the car? It's difficult to answer.
"At the same time do we know how good the Ferrari is today? Is it as good as Alonso or only as good as Massa? We don't know," he added.