That comes after his early departure during Saturday’s 2-0 win away at Sheffield United, with the Saints’ leading goalscorer coming off after just 13 minutes.
“I think it is a serious one, but not too serious,” the Saints boss said when asked about Ings’ injury. “I think three weeks it’ll be, expect him back after the international break.”
Tella is a 'jewel'
And the Austrian was full of praise for youngster Tella, who was starting only his second Premier League match on Saturday.
“This energetic young guy is one of the jewels we have in our Academy and I like to push him, because I think he showed that as a striker he is not so easy to defend,” Hasenhuttl added.
“He did exactly what we demanded of him. The stats were unbelievable, especially the high speed runs.
“We must have a look at how fit he is for Wednesday, he invested a lot and he is a young player. We must have a look in general what players are available.”
Returning from injury
Saturday also saw the return of Kyle Walker-Peters and Ibrahima Diallo, and the Saints manager was pleased with the impact they had.
“They are two players who are very important for our shape, that is a fact,” he said. “We are a different side then, this is clear. Everyone plays in his best position.
“We have to select very carefully what we do on Wednesday; sure there will be a few changes. But we want to remain competitive.”