Chelsea boss Frank Lampard says the big factor in their current form slump has been a lack of energy.
Lampard, previewing their FA Cup fourth round tie with Luton Town, says the energy with which his Chelsea team played last season was the proudest aspect he took out of the campaign.
And he stands by criticism of his players in the past week over their sluggish recent performances.
While reluctant to single out individuals, Lampard also conceded players aren't working at full capacity as Chelsea struggle this season.
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