English Premier League
Brighton vs Chelsea
Havertz and Werner are the only new faces in Chelsea's starting line-up at the Amex Stadium, with Thiago Silva, Ben Chilwell and Hakim Ziyech unavailable due to injury.
Kepa Arrizabalaga is preferred to Willy Caballero in goal despite speculation over his future, while there is also a rare Premier League start for Ruben Loftus-Cheek.
For Brighton, meanwhile, there is a debut for Adam Lallana, who joined the club from Liverpool on a free transfer at the end of last season.
Lallana is the only new signing in Graham Potter's line-up, but there is a start for Ben White, who has returned to the club following his loan spell at Leeds last season.