The Dutchman masterminded another victory against former club Vitesse Arnhem on Thursday, securing safe passage to the Europa League play-offs.
Graziano Pelle and Sadio Mane netted in a 2-0 win, taking the third qualifying round tie to 5-0 on aggregate and giving Koeman something to smile about at the end of a painful return to the GelreDome.
The Saints boss ruptured his Achilles in training on the eve of the match, meaning he took to his place on the bench with crutches and his foot in a protective boot.
Assistant manager Erwin Koeman did the post-match media activities as a result and suggested his brother may not be able to travel to Sunday's league opener against Newcastle.
"He knows he has already some problems with his Achilles and if you are involved in a training sessions then s*** can happen like what happened," he said.
"Okay, we will hear (today) what happened and we will hear (today) if he is on Sunday on the bench or not.
"(This) morning he goes to hospital and then they will decide what to do."
Fortunately for Saints, Koeman's injury is their only fresh concern heading to St James' Park - thanks in no small part to the fact the second leg often resembled an exhibition match after Pelle's early strike.
"After four minutes, it was a fantastic goal for Graziano and you know then they have to make five and it's almost impossible," Erwin Koeman said
"For us, it was a fantastic start.
"We were happy with the goal because it's all about the result and going on in the Euro League, so for us it was a fantastic start.
"The rest of the game we defended very well
They had some shots outside the 18-yard box, but I think in ball possession we did not play a good game.
"We have to improve more, especially for Sunday
We can do better and we have to do better."
It was a positive end to a day which saw unsavoury clashes between fans beforehand, with police storming in after glasses, chairs and punches were thrown in the city centre.
The incident saw 50 Dutch fans and three English supporters arrested, with a Southampton spokesman promising the club "will take relevant action against those involved".
There were no such flare ups come game-time, though, and assistant Koeman praised the 1,500 travelling fans.
"I think our supporters were amazing like last week the Vitesse supporters," he said.
"Of course they are looking forward to the draw as we also, and then going to Newcastle and it starts on Sunday.
"We are looking forward to going to Newcastle."
Source : PA
Source: PA