Despite the home side handing debuts to William Kvist and Lewis Holtby, Konstantinos Mitroglou did not make the squad and Rene Meulensteen's team suffered a confidence-shattering 3-0 loss and sank to the bottom of the Premier League table.
Here, Sports Mole takes a closer look at the match to see whether the visitors deserved their emphatic victory.
On target: 4
On target: 5
Was the result fair?
The first half was an even affair. In fact, Fulham probably edged the opening 45 minutes and tested Artur Boruc on a number of occasions. Their threat from set pieces was evident, as Dan Burn and Brede Hangeland both went close with first-half headers. The turning point came 10 minutes before the break, though. Boruc denied Darren Bent twice in quick succession, and the home side struggled to create any more clear-cut chances. Southampton stepped up a level in the second half and in the space of 11 minutes, they put the game beyond any doubt. The three goalscorers - Lallana, Lambert and Rodriguez - combined really well after the break, and it was the fluidity of their movement which gave the Saints victory today.
Fulham are in trouble. Today's result saw them drop to the foot of the Premier League table and it is not hard to see why. Bent's two chances aside, they created nothing in open play. Mitroglou has arrived with a big price tag and an equally sizeable reputation, and he will need to find the back of the net soon if the Cottagers are to avoid the drop. Defensively, they performed relatively well. Perhaps they could have done more to prevent the opening two goals, but Rodriguez's effort was unstoppable and came at a time when the hosts had to go in search of a goal.
Southampton dominated possession from start to finish, but they struggled to create much in the first half. After the break, they exploded into life. Despite injuries to Victor Wanyama and Calum Chambers, their football was sumptuous at times. Their record signing, Pablo Osvaldo, was snapped up by Juventus on loan yesterday, but so long as Lallana, Lambert and Rodriguez continue to play like this, they will not miss him at all.
Sports Mole's man of the match
Adam Lallana: It was tough to choose just one Southampton player. Luke Shaw was brilliant at left-back and it is hard to believe that he is still only 18. Morgan Schneiderlin also had a good game in the centre of the park, but Lallana was Southampton's best player. Everything good going forward came through the captain, who marked his 250th Saints appearance with a good goal this afternoon. His movement was slick and his work rate was second to none, but it was his final ball that set him apart from his peers. Time and again he laid the ball on a plate for Lambert and Rodriguez. England coach Roy Hodgson simply has to take the 25-year-old to the World Cup.
Bent's goal record over the years is pretty impressive, but the former England international missed two good opportunities before the break to give Fulham the lead. His overall performance wasn't too bad, and he showed glimpses of his predatory instincts of yesteryear, but if the Cottagers had gone into the break a goal up, who knows how the game might have finished.
The sign of a good refereeing performance is if they are not mentioned, and Mike Jones kept himself to himself on a quiet afternoon for the officials. There were not many contentious decisions, although the ball did ricochet onto the hand of Maya Yoshida in the first half and Holtby stumbled in the box under a challenge after the break, but neither warranted a penalty. A very good afternoon's work by Jones.
Fulham: Fulham welcome League One side Sheffield United to Craven Cottage on Tuesday evening in their FA Cup fourth-round replay. After the cup match, they travel to Manchester United before taking on Liverpool at home.
Southampton: Southampton are sitting pretty in ninth place as things stand, and they may well move up the table in the coming weeks. They face Stoke City at home next week, before an away game at Hull City.