The Spaniard left out several of his regular starters for Thursday's Europa League quarter-final against Rubin Kazan with this weekend's FA Cup semi-final against Manchester City in mind.
Cech believes the return of those rested players against City could be key to their chances of reaching the final as they look to retain the FA Cup.
"It was more than important. We know what kind of game is coming on Sunday and that the manager rested some players could be key," Cech told his official website.
"If you are playing for everything in three competitions, it is not easy."