Tuchel makes nine changes to the side that beat Atletico Madrid in the Champions League on Wednesday, with only Zouma and Kovacic retaining their places. Gilmour makes a rare start under the German, with Mount, Pulisic and Giroud also coming in.
SHEFFIELD UNITED SUBS: Rhian Brewster, Oliver Burke, Lys Mousset, Zak Brunt, Max Lowe, Iliman Ndiaye, Kean Bryam, Wes Foderingham, Kyron Gordon.
SHEFFIELD UNITED STARTING XI (4-4-2): Aaron Ramsdale; George Baldock, Phil Jagielka, Enda Stevens, Ben Osborn; Jayden Bogle, John Lundstram, Oliver Norwood, John Fleck; David McGoldrick, Oliver McBurnie.
CHELSEA SUBS: Timo Werner, Reece James, Willy Caballero, N'Golo Kante, Hakim Ziyech, Marcos Alonso, Antonio Rudiger, Edouard Mendy, Cesar Azpilicueta.
CHELSEA STARTING XI (4-2-3-1): Kepa Arrizabalaga; Kurt Zouma, Andreas Christensen, Ben Chilwell; Callum Hudson-Odoi, Mateo Kovacic, Billy Gilmour, Emerson; Mason Mount, Christian Pulisic; Olivier Giroud.
Hello and welcome to live coverage of the FA Cup quarter-final meeting between Chelsea and Sheffield United at Stamford Bridge!
Chelsea come into this tie in good form and are unbeaten in their 13 games under Thomas Tuchel (W9 D4), which includes a 1-0 win over Barnsley in the fifth round of the FA Cup thanks to Tammy Abraham's goal. As for United, things got off to a tough start under interim manager Paul Heckingbottom as they lost 5-0 to Leicester City in his first game on Sunday and they've won just one of their six games since the 1-0 win over Bristol City that got them into the quarter-final, losing the other five.