Mane fired a treble in two minutes and 56 seconds ??? the fastest in Premier League history ??? as the Saints kept their dream of European football alive.
The Senegal international reached double figures for Southampton with the hat-trick, and Koeman was stunned by his player???s incredible achievement.
“It’s not normal to score a hat-trick in two or three minutes, not in the Premier League, Holland or the worst league in the world,” he said.
“I speak a lot to Sadio because first of all an important thing for the player is he has to know what his best quality is and the rest of the players have to know what the best qualities of Sadio (are).
“Sometimes I have a discussion and say ‘you sometimes go down too much when backing in. You need to make movements in the space and then you are so dangerous because nobody is so fast as you’.
“He is a scorer. If you go down or to the midfield you are a long way from the goal of the opponent and you have to use your qualities.
“Today he demonstrated what we expect from Sadio. He’s a great player, a great run player in front.
“We know for some players it’s the first season in the Premier League but you have to learn and still he’s a young player and he can do much better than he did. I believe that.”
Saturday???s victory was Southampton???s first in five Premier League outings, and Koeman was delighted with an ???amazing afternoon??? on his side???s final home game of the season.
“I enjoyed it very much like all the fans because we play great football,” Koeman said.
“We had great spirit from the beginning and that was the difference between the last away games and today, and some help from Aston Villa who played offside, high defending, (gave us) a lot of space and then you have to punish that.
“It was an amazing afternoon. You don’t expect that to be honest but I was expecting a reaction of the team after the last two games.
“It was great because it’s our last home game and the fans deserved this one because they had an amazing support of the team. It was a very enjoyable afternoon.”