The Gunners go into the match against their rivals three points behind Tottenham and six off the top of the Premier League table.
Cech has been ruled out of the game with a calf injury, but is certain that Ospina will let nobody down in such a crucial game.
“David is a very experienced goalkeeper. He has played really well, especially in the FA Cup games where he has been vital,” Cech said.
“I think everybody at the club, including the staff and the players, has big confidence in him because we can see in training and in his international games that he is a great goalkeeper.
“We have full confidence in him and it won’t be a problem. He has enough experience to play this type of game and he has played this game before so I think he will be fine.
“I have to say, it is always great when you have someone with the personality [of Ospina] where he pushes you every day in training and works hard,” added Cech.
“We have a mutual support for each other and I think this is the most important in a mini group of goalkeepers - sticking together, working together and pushing each other in training. It is ideal for a goalkeeper.
“I believe this will hopefully help him as well to come in and continue his good work. He has played for Colombia in big games such as the World Cup and qualifiers and he had played the whole season when Arsenal were chasing Chelsea.
“He has enough experience to play at this level and I don't think it will be a problem for him.”Copyright 2017 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source