Pep Guardiola's side returned to competitive action on Wednesday night with a 2-0 defeat to Borussia Dortmund in the DFL-Supercup, and Lahm believes that there is still a lot of work to do before they can hit top form.
"We have a lot of players that have been in training only for a short period," the Bayern captain told reporters. "We had a lot of injured players that stayed home. That's why it was hard.
"We are in the middle if the pre-season. In training, you can only lay the ground, but not simulate the competition."
Bayern begin the defence of their Bundesliga title against Wolfsburg on August 22.