Way too early to write him off as some are doing here, and there's zero chance of Ten Hag making that mistake. He will back himself to draw out the world-beater which Sancho certainly has the talent to be. If it's an attitude problem, all the better - ETH is a man manager and attitude problems can be rectified, if anything, more easily than footballing weaknesses.
Rashford sets one example; two poor seasons, a player that unbelievably fans on here were starting to write off. Now look at him.
Antony sets another; been slow to settle in or achieve any consistency this season, but there are signs from the past few games that he's starting to click into gear (and he certainly has all the ingredients). His attitude, commitment, desire to be involved, courage to ask for the ball, defensive workrate and running have all been exemplary. Now, as it starts to pay off, he'll be a difficult-to-ignore example for Sancho; same age, also a big transfer fee, mirror positions and similar roles in the team. For a man-manager, that sort of comparison is gold-dust.