The lawyers say in papers filed this week with the trial judge that "no reasonable jury" could have found Hernandez guilty of killing Odin Lloyd in June 2013, and cite insufficient evidence for a conviction.
Hernandez was convicted in April of first-degree murder and sentenced to a mandatory term of life in prison without parole. Lloyd was dating the sister of Hernandez's fiancee.
The filing asks the judge for a finding of not guilty. The defence must take the step before an appeal, which is automatic under Massachusetts law.
Hernandez is awaiting trial in the killings of two men in 2012.