The Saints winger suffered an ankle injury in the 1-0 win over Fulham in midweek and Hasenhuttl confirmed in his Thursday press conference that the former Norwich City star has been ruled out for up to three weeks.
That news comes as a blow as Redmond has been a mainstay in the side so far this season and was the man who created the goal in Tuesday night's EFL Cup win at Craven Cottage.
It's touch and go whether striker Michael Obafemi will feature after he suffered cramp in midweek, while there are also doubts concerning Ryan Bertrand.
The defender has returned to training this week but it's unclear whether Hasenhuttl is ready to throw Bertrand back into the mix for the arrival of Manchester United this weekend.
Saints picked up their first win of the Premier League season so far last time out, as they managed to secure a 2-0 victory at Brighton.
It has been a tough start to the season for Southampton, who have faced title challengers Liverpool in their only game at St Mary's this season.
Saints pushed the Reds all the way in that 2-1 defeat and Hasenhuttl will be looking for another resilient performance when the Red Devils come to town.
"We are gaining more confidence after the last two games," he told reporters. "We have kept two clean sheets [in all competitions] and even if we have a few injuries now, we have good subs who are looking forward to playing.
"It's up to me to find the right balance and I am sure we have a squad who on the pitch can create problems. I think with Manchester United you always have pressure. I expect their best possible team to play against us."
As for United, they have picked up a couple of injuries ahead of their trip to the south coast.
Luke Shaw won't be able to face his former side as he is absent with a hamstring injury, while Anthony Martial is missing due to a thigh problem.
Diogo Dalot, Eric Bailly and Timothy Fosu-Mensah are also out on the sidelines.
United will be determined to bounce back after they suffered a 2-1 defeat on home soil to Crystal Palace last Saturday.
Manager Ole Gunnar Solskjaer could be tempted to make changes, with the likes of Juan Mata and Nemanja Matic starting the game against the Eagles from the bench.