Alex McLeish's side won 4-0 in Albania on Saturday, which puts them one win away from UEFA Nations League promotion and qualification for the play-offs for Euro 2020.
The Tartan Army were beaten 2-1 in Israel last month but the Stoke City midfielder believes they can deliver a "totally different performance" this time.
Speaking to 'Sky Sports' ahead of the fixture, Fletcher remarked: "It's going to be difficult but I think the biggest thing is they've saved a lot of legs and conserved a lot of energy.
"I don't think it was a difficult game for Scotland physically so there'll have lots of energy about them come Tuesday.
"The turnaround will be quite short but they'll be ready for it.
"It's a must win game and it gives a great chance to qualify. We knew the performance level in Israel wasn't good enough.
"We allowed them too much possession and we allowed them to control the game. We weren't aggressive enough but I think that was partly down to the formation.
"This time it will be 4-3-3, it will be pace, it will be aggressive, there will be pressing and it will be up and at them. I think you'll see a totally different Scotland performance."