Coming off an 11-3 finish, an Orange Bowl victory and a No. 8 ranking in The Associated Press' final poll, the Yellow Jackets must replace seven running backs, both starting receivers, their best guard and several defensive playmakers.
The return of junior quarterback Justin Thomas, however, gives Johnson reason to believe his spread option offense can perform at a high level in 2015.
Following the first day of spring practice on Monday, Johnson reminded the team that everyone will get enough reps to help the coaching staff gauge how the two-deep depth chart might look before the start of summer camp.
Georgia Tech will practice 14 more times before its spring game on April 17.
Johnson wants Thomas, who helped the Jackets win an Atlantic Coast Conference division title and beat Georgia for the first time since 2008, to help his less experienced teammates adjust to starting roles.
Under Johnson, Georgia Tech quarterbacks are regularly tackled while practicing the option, but Thomas will be close to off-limits this spring.
''There are clearly some things he can get better at, but we've got to be smart with him,'' Johnson said. ''We did a lot of 7-on-7 pass skill. That's always good work for him. Option read stuff is good for him. We just probably don't need to beat on him a whole lot.''
Thomas is the lone returning team captain. The team will elect two more this fall, so Thomas knows nearly everyone is looking to him as an undisputed leader.
''With the young guys out there, I need to make sure I'm on the same page with them,'' Thomas said. ''Make sure they know what they should be doing. The closer we get together and the more people that know the system and all that, we should be all right.''
Thomas believes his teammates are focused on improving this spring and not reliving the success of last season.
''You can't think about it,'' he said. ''Just have to go out there, it's a new team. We're 0-0. We've got to set a new standard for this team.''
C.J. Leggett, Dennis Andrews, Quaide Weimerskirch and Brady Swilling are the top candidates to fill the top roles at running back, but Broderick Snoddy, who is missing spring with a leg injury, is expected to return this summer and compete for a starting job.
With the top three receivers gone, Michael Summers is the closest thing Georgia Tech has to a No. 1 wideout.
Four starters return on the offensive line with Shaquille Mason now preparing for the NFL draft, though the top centers are nursing injuries and will miss all of spring.
The Jackets' defense was takeaway-savvy last year, finishing 17th nationally in turnovers forced, but it needs to improve its poor numbers on third down and average yards per play.
Johnson said that Jabari Hunt-Days, a linebacker-turned-defensive end who was declared academically ineligible last May and missed the 2014 season, was a full participant in practice.