Enzo Maresca has given Robert Sanchez the chance to prove his quality, but he has failed to live up to the coach's expectations. The decision taken by Enzo Maresca is very reasonable and previously Hansi Flick had done the same thing to Inaki Pena, now he is more trusting the main goalkeeper position to Szczesny.
Chelsea certainly won't be short of players if Robert Sanchez chooses to leave the club, there are still plenty of other goalkeepers who can be relied on to strengthen the team.
For a goalkeeper, of course, it will not be difficult for any team to find a replacement if their old goalkeeper leaves the team, but the team also needs to see a goalkeeper who has such strong reflexes because a team like Chelsea is a team that often competes in the best place so that the goalkeeper should not be taken carelessly. Although this can still be fixed very well when the goalkeeper is really trained routinely to become the best goalkeeper on the team and Enzo Maresca is also someone who is able to read the character of a player like a goalkeeper before he uses him as the main goalkeeper at Chelsea.
I don't blame Enzo Maresca for his decisions, he gave sanchez enough time to prove himself, but he couldn't so the coaches decisions is fair enough, therefore if they end up signing someone the coach feels would do better then it's not a bad idea, Sanchez in person would need to improve if given any chance before the season ends, he'll have to impress the coach if he's still interested in keeping for Chelsea, well even though he leaves Chelsea, the fact that he's played for Chelsea Fc would help him secure a move to another good team, but then he has to improve his performance so he won't suffer same fate if he moves somewhere else. Well I agree that it won't be very difficult for Chelsea to find a good replacement for Sanchez, they're a big team and many good goal keepers would be willing to go there if a better offer for them comes.