Bolt is set to defend the 100m and 200m Olympic titles he won in Beijing, where he was also a member of Jamaica's victorious 4x100m relay team.
By adding the 4x400m relay, Bolt would have a shot at becoming the first man to win four gold medals in track and field at one Olympics since Johnson's fellow American Carl Lewis achieved the feat at the 1984 Games in Los Angeles.
But Johnson, gold medallist in both the 200m and 400m at the 1996 Olympics in Atlanta, said the 25-year-old Bolt would struggle with the longer distance.
"You can't train for the 400 (as well), it would be an absolute distraction and the training wouldn't work," Johnson told BBC Radio 5 live.
"I think he could be the world-record holder at 400 metres but he's said that he has no interest in training for it, which I can understand—it's a difficult race to train for.
"I see no reason why he shouldn't be able to repeat as an Olympic gold medallist in the 100m, 200m and the 4x100m, but the 4x400m is going to be tough.
"Without him the Jamaican team certainly doesn't have enough 400m runners to beat the United States.
"They could beat the US possibly with him on the team if he was training for the 400m, but he can't just step onto the track and run a 44 or a 43-second split just off 100 and 200m training.
"I don't see that happening. I don't see the Jamaican coaching staff putting him on the 4x400m relay unproven. That means he's got to go out there and run some 400s during the season, in order to prove that he should be on that relay."