Heskey has been operating in a deeper role this season but again showed his worth during Saturday's 3-2 home win over Norwich.
McLeish admits 33-year-old Heskey is unable to complete a full game in his current condition but is full of praise for his efforts, saying: "Emile again worked tirelessly for the team on Saturday even though he has an ongoing problem with his Achilles."
He added: "The situation is such that we can't really play him for the full 90 minutes.
"But he is effective in the team with the contribution he makes and the appreciation of his team-mates for him and what he gives is there to see."
McLeish is hoping Villa skipper Stiliyan Petrov's hamstring problem, which forced him to be substituted in the second half, is not a serious setback.
He said: "Stiliyan felt a little niggle in his hamstring. He thinks he caught it just in time but we'll get him on the treatment table.
"He couldn't go on. He would have become a liability in midfield for us."