Endrick came off the bench to register against Stuttgart on Tuesday night, becoming Real Madrid's youngest-ever Champions League goalscorer in the process.
The 18-year-old has also already scored in La Liga this season, and he is putting pressure on Rodrygo when it comes to a starting role, but it is expected that he will once again be on the bench for the first whistle here.
Ancelotti may make just the one change to the side that started the 3-1 success over Stuttgart last time out, with Eder Militao set to return in the middle of the defence.
Jude Bellingham played 80 minutes of the game against Stuttgart, having recovered from an injury, and the Englishman will once again be in the XI against Espanyol.
There will be four absentees for the home side this weekend, with Dani Ceballos, Eduardo Camavinga, Brahim Diaz and David Alaba unavailable for selection.
Of those on the sidelines, Camavinga is the closest to returning, with the France international expected to be available before the end of the month.
Kylian Mbappe has scored three times in his last two league appearances for Real Madrid, and the new arrival is again set to operate through the middle for the Spanish and European champions.
Real Madrid possible starting lineup: Courtois; Carvajal, Militao, Rudiger, Mendy; Valverde, Tchouameni, Bellingham; Rodrygo, Mbappe, Vinicius