Maresca said Garnacho was ready but a tactical change and fatigue altered Chelsea's subs Saturday.
Maresca's tactics undone by an early red; Palmer played injured and Sánchez apologised on Instagram.
United held on for a 2-1 win over Chelsea at Old Trafford after red cards and late pressure tonight.
Chalobah's header gave Chelsea hope but they lost 2-1 at Old Trafford; Fernandes and Casemiro scored.
Fernandes hits century as United beat Chelsea 2-1; Casemiro sent off, Chalobah reduces late. late on.
Robert Sánchez was sent off inside five minutes, forcing Chelsea to reshuffle into five at the back.
Enzo Maresca says Ruben Amorim will face certain early struggles while adapting to English football.
Maresca says he could start Garnacho at Old Trafford but will discuss the choice with the player...
United seek response at Old Trafford while Chelsea arrive after midweek trip to Bayern Munich. soon.
Chelsea top the global squad valuations at €1.314 billion; 17 of the top 30 squads are Premier League
