A change of system has made competition for centre-back places more fierce at Stamford Bridge, with Antonio Rudiger and David Luiz seemingly Sarri's preferred partnership, but the Italian insists that Cahill remains an "important" part of his squad.
"With Cahill I think at this moment for a defender it's more difficult to play in my team after only 20 days of training," Sarri told reporters at his pre-match press conference.
"It's easier for an offensive player, but for a defender it's more difficult so at this moment he needs to have much more training with us. I told him that he needs to be patient now but that he is very important for us."
Cahill made 43 appearances for Chelsea across all competitions during Antonio Conte's final season at the club.