The Canaries lost right-back Steven Whittaker to a red card within the opening 31 minutes and the hosting Saints went on to make the most of their numerical advantage thanks to Graziano Pelle and Dusan Tadic, who scored a second-half brace.
Here, Sports Mole has looked back over the encounter to determine if the result was a fair one, or whether Norwich can count themselves to have been unfortunate.
On target: 8
On target: 1
Was the result fair?
To be fair to Norwich, when the game was 11 vs. 11, they were good value for the 0-0 draw. But, as soon as Whittaker was given his marching orders, it was pretty much one-way traffic. Southampton dominated proceedings and given the number of chances that they created, they deserved to win by such a convincing margin.
The Saints were winless going into this encounter and had just exited the Europa League. As such, there had been suggestions that confidence was low ahead of Norwich's visit. The way that Ronald Koeman's men started the game, it did same that way, but the Whittaker red card sprung Southampton into life.
It can at times be difficult to play against 10 men, but the hosts ensured that it would not be a problem by making the pitch as wide as possible. Not only did that stretch the Norwich defence, it also brought the likes of Tadic and Sadio Mane into play. From that moment, Southampton took control of proceedings and could have even scored more goals in the closing stages.
It is tough to make a fair assessment on Norwich, given that when they had a full compliment of players on the pitch, they were more than a match for their opponents. They actually created the best chance of the opening exchanges, but Cameron Jerome could not make a clean connection with his headed attempt.
After the red card, though, Norwich folded. They were pulled wide by Southampton and being a man light, it proved to be too much. Going forward to future matches after the international break, manager Alex Neil can at least take the positives from his side's display before the red card was brandished.
Sports Mole's man of the match
Sadio Mane: The winger may have been a little wasteful early on, but once he had shaken off those mistakes, he was the best player on the pitch. Although the 23-year-old did not get his name on the scoresheet, he played a key role in all three of Southampton's goals. In this type of form, it is not difficult to understand why Manchester United manager Louis van Gaal is supposedly keen to bolster his attack by signing Mane.
This can only go to one player, who will have been showered and changed before the whistle was blown for the break. Having been cautioned for needlessly stopping a quick throw from being taken, you would have expected Whittaker to be extra careful. But, within four minutes, he had received a second yellow card for tugging back Tadic.
Had the Southampton winger been through on goal, the offence would have been a little more understandable. But, there was enough cover and replays also suggested that the ball would have rolled through to John Ruddy in the Norwich goal. He can have no complaints about the sending off, which left his side, who were drawing 0-0 at the time, to play just under an hour with 10 men.
There have been some incorrect red cards dished out in the Premier League this weekend, but Jon Moss got his dismissal spot on. Whittaker's stupidity left the match official with little option but to send off the full-back. Aside from that, there was no other big calls for Moss to make.
Southampton: After the international break, Koeman's men will be on the road when they take on West Bromwich Albion at The Hawthorns.
Norwich: As for the Canaries, they will play host to fellow newly-promoted outfit Bournemouth at Carrow Road.