Barcelona coach Ronald Koeman said he was badly affected by the arrest of former President Josep Maria Bartomeu and called the man who hired him as manager an "exceptional person", while conceding the case was damaging for the club's reputation.

Bartomeu, who hired Koeman last August but resigned in October to avoid facing a vote of no-confidence, was detained on Monday along with CEO Oscar Grau in a probe related to allegations of improper management and business corruption.

The pair were released on Tuesday although the investigation, which began last year before Koeman joined as coach, remains open.

"When I heard the news I was devastated because I know Bartomeu and Grau well," Koeman told a news conference ahead of Barca's Copa del Rey semi-final second leg at home to Sevilla, when they will be hoping to overturn a 2-0 deficit.

"I feel bad for them, I had good moments with them in a short space of time and Bartomeu has always been an exceptional person to me.

"It's not good for the image of the club but we have to wait and see what happens (with the investigation). I wasn't here then so I can't talk about it, we just have to focus on our job and in turning the tie around tomorrow."

Barca have been in the hands of an interim management committee led by acting President Carles Tusquets since Bartomeu resigned but members will elect a new leader in an election on Sunday.

Bartomeu's arrest is the latest episode in a long line of institutional problems the club has experienced in the last year, including a growing financial crisis, but Koeman said he had no regrets in accepting the job as coach.

"You never know what's going to happen in the future. When Barca called me I was convinced I had to take the job," he said.

"I knew it was a difficult moment, the club was losing money and had to make changes to the squad and put its faith in young players but I have tried to do my best and what I felt was right. Life is full of ups and downs and opportunities and problems and you have to try and resolve them."

Barca beat Sevilla 2-0 away on Saturday in La Liga and have been boosted by teenage midfielder Pedri making a quick recovery from a muscle injury although defender Ronald Araujo is a serious doubt.