Benteke recently put in a transfer request at Villa Park having joined from Genk last summer.
"We have not been given much information about why he is not joining us for pre-season but apparently he has put in a transfer request," Helenius told the Birmingham Mail. "It is not something that I take much joy from even though it improves my chances.
"We need the strongest possible squad for the upcoming season and I was looking forward to being in the same side as Christian Benteke.
"In that respect it is sad what is happening around Benteke as he was definitely one of the players that I was looking forward to observing and learning from."
Chelsea and Tottenham Hotspur are both reported to be interested in the Villa forward.