Austin completed a move from QPR last weekend and has been put through his paces at Southampton’s Staplewood Campus this week.
Koeman has been pleased with what he has seen from the 26-year-old and expects him to be part of the squad for the Barclays Premier League contest at Old Trafford.
"His fitness is ok,” Koeman told youtube.com/southamptonfc
. “I was a little bit worried about his fitness, because he came out from a hamstring injury, but he showed his quality, he showed his fitness this week, and normally he will be part of the team for this Saturday.”
Having had a full week to work with Austin, Koeman explained how impressed he has been with the forward’s ability and attitude.
"It's very good,” he said. “Of course, you analyse the player, you know why you like to buy that player, because of his number of goals, but his whole attitude – I spoke to Charlie two weeks ago and that's important to have really a good impression, if you talk about football, but also about other things out of football, because I like to have a talk to the player and to have really a good feeling about the player, then the possibility that everything goes well is ok.
“He showed personality and on the pitch this week he showed his qualities and he's a very good signing.”
Elsewhere, Saints will continue to assess the fitness of striker Graziano Pellè, as he works his way back from a knee problem, while Matt Targett will also be watched closely.
"We have some small problems with players like Graziano, if he is really fit to be part of the team,” said Koeman. “Matthew Targett had some little stiffness about last weekend, and tomorrow we have our final session, then we make those kind of decisions.”