That's a very valid concern, however, what makes me hopeful comes back to what ETH said about attitude. There's been an injection of new personalities, and I like what I've seen from the.
I can't see Martinez, Malacia, and when he comes in, Casemiro strolling about the pitch in any game - it's not in their nature. Add Fred (yes) to that, and that's a good number of natural fighters on the pitch - which we've sorely lacked.
Hopefully those fire up the rest like Sancho and Rashford (who worked really hard and even contested for aerial balls and won some against the CBs!!!)