Newcastle threw away an advantage against Queens Park Rangers at the weekend.
Riviere was talking after Newcastle's 2-1 loss to Queens Park Rangers at the weekend and gave his assessment of where things went wrong.
The French striker maintained that a tactical change which QPR made at half-time turned the game and Newcastle didn't respond in time.
“We had a good first half, and after QPR changed tactics, fought well and scored two goals,” he said.
“QPR changed with a 4-4-2 and we didn’t quickly enough change our tactics. We have to focus so that can never happen again."
It is true that Newcastle appeared to lose focus after Carver's half-time team talk, as they had looked in control of the match during the first 45 minutes.
Newcastle dominated the opening period, but they could not deal with QPR in the second half and that is very worrying, considering the London outfit had little to play for in the fixture.
QPR's victory means that Newcastle have now gone 10 games without winning and their Premier League status is still far from secure.
If Hull City beat Manchester United on the final day then Newcastle will be required to be triumphant against West Ham United to stay up.