Arsène Wenger has confirmed David Ospina will start against Östersund in the Europa League tonight and Manchester City in the Carabao Cup final on Sunday.

The Arsenal manager admitted it was tough to overlook his first-choice goalkeeper, Petr Cech, for the Wembley final but he has refused to deviate from his policy of starting Ospina in the cup competitions.

Ospina, whose contract is due to expire in the summer of next year, has played – when fit – in all of Arsenal’s cup games this season. The Colombia No 1 missed three of them because of groin trouble from mid-October – the home and away Europa League ties against Red Star Belgrade and the Carabao Cup home win over Norwich City.

Wenger turned to Cech in Belgrade and Matt Macey in the other two games. He also started Ospina over Cech in last season’s FA Cup final victory over Chelsea. “They are always difficult decisions but we have been clear since the start of the season that he [Ospina] plays in the whole competition,” Wenger said, with regard to his Carabao Cup final selection. “I have two world-class goalkeepers and I decided to have clarity in the games they play and we maintain that.”

Wenger will make sweeping changes to his lineup against Östersund at the Emirates Stadium, with his team 3-0 up in the Europa League last-32 tie. In the absence of the cup-tied Pierre-Emerick Aubameyang and the injured Alexandre Lacazette – he underwent knee surgery last week – there will be an opportunity up front for Danny Welbeck.

Wenger reflected on the traumatic time Welbeck has endured since signing from Manchester United in September 2014; the striker missed 17 months with two separate knee injuries and there have been further layoffs because of muscular problems. But Wenger claims to have seen signs of the Welbeck from 2014‑15, when the player scored six goals for England, including two in the 2-0 away win over Switzerland in Euro 2016 qualification.

It was put to the Arsenal manager that Welbeck might have lost his confidence for a time because of the injuries. “I would not disagree with you on that,” he said. “I remember when he played for England in Switzerland and he looked absolutely marvellous. I see signs of him now in training when he is like that period.

“It’s difficult to imagine a guy who has basically been one and a half years out – that’s absolutely traumatic. You lose faith in your body. One of the advantages of being young is that you feel undestroyable. It gives you an arrogance but as soon as your arrogance is hit, you are lost. You can get it back but it takes time.”

Welbeck is approaching the final 12 months on his contract and Wenger said he wants to tie him down at the club for longer. He added that the way Jack Wilshere had recovered from long-term injuries could serve as an inspiration to Welbeck.

Mesut Özil will not play against Östersund because he had fallen ill again over the weekend. The midfielder returned to training on Wednesday and will be fine for the League Cup final.

“His immune system is a bit in trouble at the moment and I don’t know why,” Wenger said. “We hope we can improve that medically.”

Aaron Ramsey remains out with a groin problem, although he trained on Wednesday and Wenger has refused to rule him out for Sunday. Henrikh Mkhitaryan, who is cup-tied in the Carabao Cup, will start against Östersund. Wenger also offered an update on Lacazette. “I think he will be ahead of the planned recovery,” he said. “It should be four weeks, maybe three and a half.”