The Belgian picked up a back injury during the Chelsea's 2-2 draw with Manchester United and with a quick turnaround before their Premier League fixture at Turf Moor on Saturday, Sarri will also take the opportunity to rest Jorginho.
Chelsea had several chances to extend their lead through Willian, Pedro and Olivier Giroud but the Blues maintained their 2-0 lead until the 54th minute when Loftus-Cheek ensured he'd be going home with the match ball.
The Italian has so far overlooked Loftus-Cheek since arriving in west London, reducing him to just two starts so far this term.
Talented teenager Callum Hudson-Odoi has had some interest in both loan moves and a permanent transfer as January approaches too, but he has been cautious about signing onto a new Chelsea contract without confidence that he will get game time in the first team. They've not been easy.
Just before the end of the second time, Alexandr Hleb - back with BATE Borisov for the fifth spell of his career - briefly left the pitch suffering with an injury, with little sympathy for the ex-Arsenal man from the partisan home crowd.
"This match is not a big problem, because we have to play after five days, from the last match", said Sarri. We have to change something.
The left-back, who began his career at Real Madrid, made his global debut in March this year and has won three caps to date.
BATE manager Alyaksey Baha: "We have followed all the games Chelsea have played".
This will be Chelsea's first meeting with Belarusian opposition. However, just 10 of these have been on target (20%), with just two finding the net (4%).