The phrase "not shrewd enough" is grammatically correct and can be used in written English.
It is typically used to describe someone who is not cunning, clever, or sharp in their thinking or actions. Example: "Despite his experience in business, John was not shrewd enough to negotiate a good deal for himself."
The film glorifies the horse's questionable exploits and endurance: he's certainly smart enough to have typed it, not to mention shrewd enough to keep quiet.
But the 35 co-operatives that now mine mostly lead and zinc are unregulated, pay no taxes and critics say they exploit those miners who aren't lucky or shrewd enough to have become co-op bigwigs.
As always, he said he would not let the outside commotion influence him, although he is shrewd enough not to let on if it did.
Benitez is and, while Franco is shrewd enough not to grouse publicly, it bothers him that he is not closing and it bothers him when the Mets fans treat him like he is wearing a John Rocker mask.
But Mr. Whitaker was shrewd enough not to take his own carefully cultivated legend too seriously.
Despite his anger, French is shrewd enough not to venture an answer.
Nevertheless, a few cabinet ministers took opposing positions on the re-enactment.Quebec's premier, Jean Charest, was shrewd enough not to get involved.
Professor Berman is shrewd enough not to repeat the left-wing fallacy that terrorism itself is a product of economic deprivation.
Vettivetpillai is shrewd enough not to comment too deeply on recent controversy over the near-£1m salary of CDC's chief executives.
Manager Joe Torre was shrewd enough not to try to squeeze another inning out of a suspect starter when the Yankees have a superb bullpen.
But although the former governor and self-described "hockey mom" from Alaska captured the headlines, she was shrewd enough not to claim leadership of a movement that is suspicious of leaders.
