When Mauricio Pochettino held his press conference on Friday, there was no mention of any injury concerns over two of the club's most expensive-ever signings.
However, the Argentine midfielder and Ukrainian winger are notable absentees as Pochettino makes a total of three changes from the 2-2 draw against Arsenal.
As well as Fernandez and Mudryk, Malo Gusto also drops out of the team, his place being taken by Axel Disasi who will seemingly line up at right-back.
That said, it is plausible that Marc Cucurella could switch to that role and Levi Colwill move back out to the left, with Disasi and Thiago Silva being deployed in the middle.
Noni Madueke and Nicolas Jackson are also included in the side, the former making his first Premier League start of the season.
Jackson dropped down to the substitutes' bench last weekend having had minor wrist surgery during the October international break.
Reece James, as expected, only features among the replacements, with there being an inexperienced feel to Chelsea's attacking options with Ian Maatsen yet to make a Premier League start in 2023-24 and youngsters Alex Matos and Deivid Washington having just one minute between them.
Meanwhile, Brentford head coach Thomas Frank has made two alterations to the side that started the 3-0 victory over Burnley.
Aaron Hickey returns after a one-match ban and Mads Roerslev comes into the back five, with Frank Onyeka and Neal Maupay only being selected on the bench.
Chelsea: Sanchez; Disasi, Silva, Colwill, Cucurella; Caicedo, Gallagher; Madueke, Palmer, Sterling; Jackson
Subs: Petrovic, Beach, Gusto, James, Badiashile, Maatsen, Ugochukwu, Matos, Washington
Brentford: Flekken; Roerslev, Ajer, Collins, Pinnock, Hickey; Norgaard, Jensen, Janelt; Wissa, Mbeumo
Subs: Strakosha, Maupay, Zanka, Ghoddos, Onyeka, Mee, Yarmoliuk, Olakigbe, Brierley