Mane was dropped from the starting line-up two hours before kick-off, having arrived late for a team meeting.
And Wanyama’s 74th-minute red card was swiftly followed by Alex Tettey’s winning goal, leaving the Saints with six defeats from their last eight league fixtures.
“I feel let down by some players, yes of course — because we had a different line-up for the game,” said Koeman. “Sadio was in to start but we have rules in the team and he did a big mistake before the game in our last meeting. He came late and that’s impossible. Everybody knows that we have a sanction — you don’t start. So then you have to make changes in the team, changes to all the set-pieces, everything. I don’t understand a player that comes in late to the last meeting. You will have to ask him why. I don’t know. I didn’t ask — otherwise then you get into details and it is already too late.” Koeman acknowledged it was the second time Mane had received the sanction.
“My message to Sadio two days ago in training was that I didn’t think he was really focused and concentrated.
“Yes I feel let down by him, but it’s felt much more by his team-mates because we are a club where we like to treat everybody very respectfully and you have responsibilities as a player, to the fans, to your team-mates, to your board, to the technical staff.
“We had a great talk from our chairman on Friday about the club, the team, about the respect, the ambition, the spirit, focus, concentration. And then this happens.
Southampton had the lion’s share of control and chances at Carrow Road until being reduced to 10 men, but now find themselves just a point ahead of their newly-promoted hosts, to the delight of Canaries manager Alex Neil.
“I’m over the moon with the boys in particular, because when you are going through difficult spells, there have been questions posed about them and me — and the best way to deal with it is to win games. We’ve won some crucial games now and kept two clean sheets as well, so there are a lot of positives to take.”
Rudd, Martin, Bennett, Bassong, Brady, Redmond (Odjidja-Ofoe 63), Tettey, O’Neil, Hoolahan (Olsson 82), Howson, Mbokani (Jerome 81).
Ruddy,Whittaker, Dorrans, Mulumbu.
Stekelenburg, Martina, Fonte, Van Dijk, Bertrand, Wanyama, Clasie (Reed 80), Ward-Prowse (Ramirez 87), Steven Davis, Tadic (Mane 80), Long.
Yoshida, Gazzaniga, Targett, Seager.