Widespread talk of a meltdown during the summer has proved laughably wide of the mark, yet even the most optimistic of Saints fans could not have predicted the side lying second as December approaches.
Koeman's men have been so impressive that they are considered to be genuine contenders for a Champions League berth, although the doubters will point to the level of opposition as a caveat to this term's success.
Manchester City's arrival at St Mary's on Sunday will undoubtedly be their biggest test to date and one which is followed by a midweek trip to Arsenal and home clash with United.
That hectic schedule, which will only get worse over the coming weeks, is a new experience for Koeman, but one the widely-experienced former Holland international is relishing.
"I feel happy and not afraid for this week," the Saints manager said
"I am positive and I know that we have a strong team and that we can beat everyone in the Premier League
We have to show it and in football, you never know.
"You have to prepare yourselves, to keep your way of playing and don't change if the opponent is City."
Manuel Pellegrini's side come into the game buoyed by a remarkable Sergio Aguero-inspired 3-2 win over Bayern Munich in the Champions League, whereas Saints were held to a 1-1 draw at Aston Villa on Monday.
It brought a five-match winning streak to an end and, considering they remain unbeaten, Koeman was impressed by his players' frustration.
"We are growing up because everybody was a little bit disappointed after last Monday," he said
"That says a lot because it's not a bad result a draw away against Villa, but we had a little bit of a feeling it was not good enough.
"That's a good quality to realise that and that means a lot, but it's nice to show the qualities and there's always more attention if you play City at home rather than another team."
It is the kind of mentality Koeman knows is important to cultivate, having won titles with some of Europe's biggest clubs as both player and manager.
In fact, maintaining it is the only real concern the Dutchman has when it comes to challenging the traditional powers of English football, such as Sunday's opponents.
"It's difficult because they have that experience and we don't have that experience," the Southampton manager said.
"We have experience in the Premier League but we don't have the experience that you play every three days on a high level.
"They are always under pressure in Champions League and Premier League and fight for the title and if they slow they have critics and they are used to that
The coach is very experienced and it's not a problem."
While Saints' naivety may work against them, they do having a helping hand in their top-four tilt.
Unlike their rivals, Koeman's men are unburdened by European football - something which last season helped Liverpool come agonisingly close to ending their wait for the title.
"We have the whole week of training," Koeman said "It's different in the situation of Liverpool [this season] because they play Champions League and we have the whole week like United.
"We will see at the end of the season but you don't have time in football.
"Everybody needs time if you change the team but you play every weekend and you have to win and take points and that's football."
Source : PA
Source: PA