The Clydesdale Bank Premier League winners signed off their campaign with a trip to Norwich for Adam Drury's testimonial, where a mixed side went down 2-0.
When the Celtic squad return from their summer break, there will be little time to ease the group back into action, with the small matter of a potentially tough European tie looming at the start of August. Lennon said: "It is a very difficult scenario you face when your first competitive game is going to be a Champions League qualifier."
He added: "You could get a team who may be five or 10 games into their season, who are up to match speed.
"It is always a tightrope which you are walking, so we have worked with the players over the last few weeks of the season, with plans for them to do over the summer.
"Obviously we want them to have a break as well, they have earned that, but we want them to come back in at a pretty decent level of fitness for the start of pre-season again."
Celtic have several players out of contract this summer, with Lennon looking to trim his squad as well as bring in targets such as Norwegian midfielder Markus Henriksen from Rosenborg.
"I have a lot of work to do," added Lennon. "You enjoy the trophy celebration for a day or two, and then you start planning for next year.
"We will be trying to offload a few players in the summer and maybe add two or three."