Southampton's Shane Long celebrates scoring
It's yet another huge loss for Southampton having suffered some key departures in the last two years, from manager Mauricio Pochettino to a host of key players, including Nathaniel Clyne, Dejan Lovren, Luke Shaw, Morgan Schneiderlin, Adam Lallana and Rickie Lambert.
Koeman fought through the losses, and whilst Southampton must now look for a replacement as the Dutchman's move to Goodison Park draws ever closer, they may also lose some more players.
The Mirror report that Saints chiefs are worried about the future of striker Shane Long, and believe that Koeman and Pochettino will look to swoop on their former employers with moves for Long this summer.
The Republic of Ireland international enjoyed his finest Premier League season of his career with ten goals, whilst he also added another three goals in other competitions.
The 29-year-old is being offered a long-term deal by Southampton, but it's claimed that Koeman's departure means that certain players are re-considering their futures at St. Mary's Stadium - and Long is one such player.
With Everton under Koeman and Tottenham under Pochettino believed to be keen on the pacey, hard-working forward, this could be another summer of departures for the Saints; but as they've proven over the years, they can bounce back from anything and continue to thrive in the top flight.
Do you think Long will leave Southampton this summer?