That’s the belief of Reds legend Graeme Souness.
Liverpool lost 2-0 in Serbia at the Marakana courtesy of a Milan Pavkov brace – a header at a corner and a drive from 25 yards which Alisson couldn’t get to in time.
Klopp made three changes to his starting line-up for the Champions League tie with Daniel Sturridge, Adam Lallana and Joel Matip coming in for Firmino, Fabinho and Gomez after the draw at Arsenal at the weekend.
But he brought on both Firmino and Gomez at half time with Liverpool struggling.
In the build-up to the clash in Belgrade, Klopp told reporters he had “no concerns” over Firmino’s form despite scoring just one goal in his previous nine appearances – that in the previous meeting with Red Star at Anfield.
And pre-match Klopp explained that Lallana was “ready” and that Gomez was fine but had missed training the day before with a “little issue”.
Yet ex-Liverpool captain and manager Souness thinks Klopp made a mistake in not keeping the pair in his starting line-up.
“I think not starting with Firmino or Joe Gomez,” the pundit told Virgin Media One when asked where it went wrong for his former club.
“The fact they were on the bench and came on half time suggests they were fine so it wasn’t them carrying something.
“I think the message it sends to the rest of the players was, ‘You won 4-0 last time we’ll be fine again tonight.’
“I’m of the belief you start with your strongest team, get the game won and then get off the players you want to rest.
“I think that message by not picking your strongest team to start with would have an effect with some of the players who did start.
“They weren’t at it. They didn’t start right and when you don’t start right, it really is an uphill battle to get the momentum back again.
“I felt they handed the momentum to Red Star and they managed to keep it for the rest of the game.
“They’re not at the level they were at last year, Liverpool.”
Liverpool’s next match sees them face Paris Saint-Germain away from home having downed the Ligue 1 champions 3-2 at Anfield in September.
If Liverpool win in Paris, they will progress. If they draw, then they must beat Napoli in their final game in December – whereas defeat to PSG would mean they must beat the Italian side by two goals on Merseyside.