Just looked at a few of the games from the run last season (these are just the ones I spotted, may have missed some absentees):
Southampton: Missing Coleman & Richarlison
Newcastle: Missing Richarlison, Godfrey, Digne, Coleman, James, with Pickford out of the team
Man Utd: Missing Richarlison
Fulham: (won)
Leeds: Missing Digne & Coleman
Not necessarily blighted, but hardly "a largely fully fit side"
Ancelotti also gave the impression that he knew what the issue was, talking about stabilising the defence. After that run we beat Chelsea, Leicester and Arsenal on the spin, conceding a total of 1 goal.