Arsenal manager Arsene Wenger has described David Ospina as world-class and confirmed his second-choice goalkeeper will start against Sunderland in the FA Cup this weekend.
Ospina has yet to feature in the Premier League this season due to Cech's impressive form since arriving from Chelsea in June, with the Colombian's only match action coming in the League Cup and the Champions League.
An own-goal in Arsenal's 3-2 defeat to Olympiacos prompted criticism of Ospina - and of Wenger for resting Cech - but the Frenchman remains confident in his number-two goalkeeper.
"Ospina will play. I believe that Ospina has not been treated fairly. If you look at the whole of 2015, everybody neglects how well he played for six months," he told reporters.
"I personally think he is world-class. I did not take Petr Cech based on the performances of Ospina. Petr Cech was just an exceptional opportunity where it was difficult to say no.
"It was not because I was unhappy with Ospina. I was very happy with Ospina. It was just an opportunity to say no would not have been right. Unfortunately, Ospina has been punished by that decision. I rate him highly.
"True, he had a bad season, because he has that mistake [against Olympiacos] and when you do not have many opportunities and you have one bad catch, everyone is after you. But if you look at his performances from January to the end of the season, he saved us in many games.
"He is a top professional. We are lucky because he has a top attitude, very intelligent, very brave, very quick, difference with Cech is he has less experience and his size. Cech is so tall that when he stretches he covers more surface.
"It is a special position, it is an under-rated and unfair position - a striker always gets more credit than a goalkeeper. A goalkeeper keeps you three times in a game, a striker scores a goal in a 1-0 win and even if he misses four chances the next day everyone speaks of the striker and forgets that the goalkeeper saved you the game."
Arsenal are seeking to become the first side in over a century to win the competition three times in a row and begin their defence against Sam Allardyce's Premier League strugglers.
Having tasted success at Wembley in each of the last two seasons, Wenger continued: "The FA Cup is something special. Everybody loves it. It's a dream to win the Cup. I was lucky I won it everywhere [with Nagoya Grampus and Monaco].
"It's a consequence of the fact that I prepare my team in a focused way for every competition. Three times [in a row] would be great, but one of the most difficult rounds is the third round.
"Once you are in the competition, the players get slowly in it but the first game is always a bit difficult to get in there."