That is the opinion of Anfield legend Jamie Carragher.
Liverpool face Tottenham on Saturday afternoon, as well as Paris Saint-Germain, Chelsea, Napoli and Manchester City in the next month.
Last season Liverpool finished fourth in the Premier League, but struggled against their Big Six rivals, especially on the road.
They conceded 15 goals in those five fixtures, and were thrashed by Manchester City and Saturday’s opponents, Spurs.
Jurgen Klopp’s men have begun this campaign strongly, sitting atop the Premier League after four games, but Carragher believes their mettle hasn’t been truly tested yet.
“Good as it has been so far – with respect – they have not come up against a team of Spurs’ quality yet, nor a striker of Harry Kane’s class,” Carragher wrote for the Telegraph.
“He tortured Liverpool in this fixture a year ago, forcing a defensive substitution when Dejan Lovren was withdrawn before half-time.”
The Reds’ backline has been embellished since then with the acquisitions of Virgil van Dijk and Alisson Becker – signings which former centre-half Carragher regard as invaluable.
“The modern centre-back at an elite, Champions League club needs to multi-task, capable of playing a high line with the pace and strength to regularly deal with one-on-one situations,” he added.
“Full-backs no longer stay deep to assist centre-backs. They are judged on the number of crosses they make, not block.
“There is less central midfield protection with the team pressing so high up the pitch.
“Van Dijk has brought assurance, making the difficult look easy. He gets his head onto set-pieces, has a positive effect on those around him and reduces periods where the defence looks under the cosh.
“The expectation is Van Dijk and Alisson Becker will make the difference. Liverpool have only conceded once – and that was from a daft, avoidable error against Leicester – so the signs are promising.”
To sustain a title challenge, Carragher would like to see more controlled games against rivals.
“So many Liverpool games in the Klopp era have been like basketball matches, flowing end to end,” Carragher continued.
“Think of the Arsenal away match last season, Liverpool ahead thanks to scintillating attacking football – but so vulnerable they still drew 3-3.
“There have been too many examples like this. It is exciting to watch, but not title-winning football.
“A brilliant strikeforce will win plenty of games and admirers, but you cannot win the title without a strong defence.”