Long has scored three goals and registered three assists in Saints’ last four games, helping Koeman’s team to 10 points from 12 in that run.
The 29-year-old managed just five goals in the Premier League last season, his first at St Mary’s, and his manager is delighted with the improvement of a striker never considered much more than a workhorse.
The Dutch boss said: “I remember when Shane came, I think in all aspects he has learnt a lot.
“We did a lot with Shane in a lot of aspects of football and I think he is more complete as a player, as a striker.
“His pace, his timing, his movements are full of confidence. It is a big example that you can still learn when you are 26, 27, 28. You can learn every day.
“It is a big example of how you can develop with the help of coaches and that is nice to see.
“He was always really excited to come to Southampton and I remember talking to Shane about training sessions, ours are a little bit different to the usual English striker.
“He is really complete as a striker, in the box he is clever, he has a really good header, he makes it so difficult for the defenders because he is always on the move.”
Koeman takes his team to White Hart Lane on Sunday, as the Saints face off against Tottenham – the only team the Dutchman has failed to beat since taking charge on the South Coast.
A win in North London could move his side into fifth place, and Koeman remains determined his side have a chance of playing European football next season.
If Liverpool beat Sevilla in the Europa League final and Manchester United beat Palace in the FA Cup final, eight English teams will be competing in Europe next season, but the Dutchman doesn’t want qualification out of his hands.
He said: “(Eight teams in Europe) would be great news for us and great news for English football.
“I was very happy about the final result of Liverpool. It is great for Liverpool and good to have an English team in the final.
“First of all, if you can do it by yourself that is the best but if we need any help then we would like to have it.
“The team is full of confidence. We don’t have injuries and the team is working hard, keeping the belief and keeping fighting for Europe. We are still in charge of that.”