Sadio and Mo are not "wide players". Look at their position for almost all of their goals - in the penalty area. I do think Rhian can help keep those two rested and make an inpact himself.
Bobby plays a position almost unique to world football let alone the Premier League. Minamino's last sub appearance was a bit more promising than those he made beforehand, but he's light years away from showing he could be cover for the Bobby of the past three seasons.
I don't understand the thinking of people who see everything as an old 442, when we play a modern 433.
Mane and Salah are not even wide forwards, and our play is more like an inverted triangle most of the time up top when Firmino drops deep.
It's like the "we need a midfield playmaker" argument, when our 3 midfielders are primarily defensive and the FB's are the creators, with the assist stats to prove it.
Even our default formation could hardly be described as rigid, and it shifts and changes throughout a match.