To be fair, most of us would have had our three top CMs down as Bentancur, Bissouma and PEH at the start of this season, with Skippy in 4th, just because he'd been out for so long. Remove two starting CMs from almost any team (exceptions being Emirates Marketing Project and Arsenal, I guess) and there's trouble ahead. If not dropping a long way down the selection list, then messing around with formations to cover the gap.
Instead, Sarr has been a very welcome bonus and, to be honest, I trust Skippy to come in once he's match fit. Could do a lot worse than those two and PEH.
IMHO, the key to getting back into the top 4 will be the availability of Romero and the form of our forwards, not whether Sarr and Skipp can work the midfield. Although luck certainly seems to be against us at the moment.