"December-January," Klopp told British media when asked what was the biggest lesson he learned during Liverpool's poor run.
"In December we missed players and did not have the best schedule. You could see the difference physically."
Liverpool's title bid has collapsed in recent weeks as they have dropped to fifth, 11 points behind leaders Chelsea after 25 games.
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"It was a few things. On a few things we had an influence and on others we did not have an influence -- we conceded goals, offside against us, penalty against us," Klopp rued.
"We could have had two, three or four points more. We are not used to being a top team, maybe we have to be. We are not clever like Chelsea who will be 2-0 up and just finish a game."
Liverpool, who are on a five-day training camp in Spain, travel to 17th-placed Leicester City in the Premier League on Feb. 27.
(Reporting by Shravanth Vijayakumar in Bengaluru; editing by Sudipto Ganguly)
