be slipping

be slipping

To fail to do something as well as one normally does. This dish tastes strange—I think the chef is slipping.
See also: slip

be ˈslipping

(informal) (of somebody’s behaviour or performance) not be as good, tidy, efficient, etc. as usual; not be up to somebody’s usual high standard: You’re slipping, Edwina: this letter is full of typing errors.That’s three times he’s beaten me — I must be slipping!
See also: slip
References in classic literature ?
I think he must be slipping," at last I heard him sigh.
He wanted to gulp in a few last breaths of tranquillity before the tension of a season that seems to be slipping away from him began to tighten its grip again.