This season should still be fine. Henderson is still untested at the Top-6, mind. He will most likely be a Cup GK initially, taking on the Romero role (who is likely to be moved on). Which is fine. And if DDG regains his confidence, nothing like it. Still prefer him over almost any other GK for pure GK skills (ignoring the Sweeper role).
If not, won't be too much of an issue to sell him on, without taking the brunt of the wages (depends on how Covid goes and club finances). I mean, it's not a Kepa situation where he makes atrocious errors. For DDG, I reckon it is more of a confidence issue. Wages could be a concern, but I'm not as worried as I would be a la Sanchez.
And to be fair, he was in his prime when our defence was leaky AF, so he was facing more shots very regularly. This was something that was reduced last season, making it harder on the concentration, I guess.