Austin headed home within eight minutes of coming on against Manchester United, as Koeman’s men made it back-to-back victories away to Louis van Gaal’s side.
Saints boss Koeman was pleased to see his latest recruit make an immediate impact and earn the visitors a huge three points.
“It was fantastic. I said to him to play in front with Shane and when he came onto the pitch it was a free-kick,” Koeman said when talking to youtube.com/southamptonfc
“I said ‘okay, it’s nice to come on the pitch and score’, but it was a little bit later that he did.
“He has big numbers in scoring goals and he showed that. It gives competition to everybody and it’s a great signing. It’s great to work with those kind of players.
“It was a great debut for him on a personal aspect, but the whole team – how we work together and the organisation – is a big compliment to everybody.”
Saints fans were chanting for Austin’s introduction for some time before Koeman replaced Sadio Mané with the 26 year-old, and the boss explained why he waited until the 79th minute.
“We know he had a good week training, but he’s coming out of an injury and he didn’t play for five or six weeks,” Koeman added.
“Then you have to be a little bit patient, but he had 15 minutes with the extra time. It was a great goal and a big win.”