The Saints are still negotiating with the four-time European Cup/Champions League winners but it is looking seemingly likely that the midfielder will depart St. Mary's this summer; which will be nothing less than a major blow for boss Mark Hughes.
Tadić is currently on international duty with Serbia at the 2018 World Cup, starting in his country's opener against Costa Rica which they won one goal to nil courtesy of former Manchester City man Aleksandar Kolarov's superb free-kick.
Dušan Tadić has also played in the Netherlands before; plying his trade at Groningen and FC Twente prior to his move from the latter to Southampton four years ago.
How much of a miss will Dušan Tadić be to the Saints?
It is without denial that the 54-capped international has played an integral in Southampton's team since his arrival, and was pivotal in the club's top-flight survival last campaign; Tadić netted a brace in Hughes' side's 2-1 victory over AFC Bournemouth in April - a result which very well kept the team in the Premier League for another season.
The wide midfielder, who has also amassed a number of appearances playing in a central attacking role, was the Saints' joint top scorer in the 2017/18 campaign, tallying up seven goals in all competitions from 41 appearances as well as accumulating four assists to add to his Southampton career total.
Whilst he still remains a Saints player, it appears to be only a matter of time before Dušan Tadić is confirmed as an Ajax player and will be able to provide plenty of top-flight experience to his game in the Netherlands having racked up over 9,600 minutes in English league football.
Mark Hughes desperately needs to draw up potential replacements
Southampton supporters will certainly want to be in denial that this news has come out but the realistic situation is that Dušan Tadić's days on the south coast are numbered and the club are yet to acquire any summer signings; lacking behind several of their Premier League rivals.
West Ham United have already added Issa Diop to their ranks for the upcoming season and Leicester City recently made their third addition of the window, signing Southampton target James Maddison to the Foxes' squad.
Mark Hughes may be looking at the European market, or could dive into his former employer Stoke City, where Xherdan Shaqiri suffered relegation to the Championship, but the Saints boss may wait until Switzerland's World Cup campaign comes to an end before making a move for the Swiss international.
There has also been brief reports that Celtic midfielder Stuart Armstrong is on Hughes' radar this summer, however, fans may be sceptical with the 26 year-old's arrival has the Scottish Premier League is not as much a competitive division as the English top-flight.
Dušan Tadić is on his way out of Southampton and whoever the potential replacement is, manager Mark Hughes has to act swiftly to display his intent at making an impact on the south coast to avoid another disastrous season, as they dramatically experienced last term.