Fletcher is back in the squad for the first time since November 2012 after battling back from a chronic bowel condition to return to the Manchester United team.
Manager Gordon Strachan is yet to confirm whether the 30-year-old will play in the friendly on Wednesday night or re-assume the captaincy from Scott Brown, but Bannan is delighted to have the team's natural leader back in the fold.
The Crystal Palace midfielder, speaking from Glasgow Airport ahead of the squad's departure, said: "He's like the daddy of the team. You look up to him because of what he has done and just to have him back is a big, big boost for the whole country.
"I was young when I first broke through and he was one I was kind of in awe of and looked up to. He made it so easy for me. It's good to have him back. He's the captain and the leader."
Bannan believes victory could give Scotland a psychological boost ahead of their return trip to Warsaw for a European Championship qualifier in October.
The former Aston Villa midfielder said: "Obviously it has come around that they are going to be in our group so we will get a good look at them and they will get a good look at us as well.
"But it could give us an edge going into the group stages if we get one over them now. I think we can learn a lot, obviously depending on the result."
Bannan is keen to build on recent momentum. Strachan's men have won three and drawn one of their previous four matches, and have won in Croatia, Macedonia and Norway over the past nine months.
"We are always looking to improve," Bannan said. "We have had some good results recently and it's been a while since we last met up and played so we are looking forward to putting in another result and solid performance.
"We have been playing really well since the gaffer has come in really. Everyone that comes away now is just looking forward to playing now because we are high in confidence and hopefully we can keep that going."
Bannan has not played for Palace for a month but Strachan kept faith with him previously when he was out of favour at Villa.
However, the left-sided player feels the current squad is as strong as it has been and knows he will have to be at his best in order to stay in the team.
"Every game you are fighting for your place," he said. "There are a lot of good players here and it's a strong squad now. You can see there are some good players left out that have been unlucky.
"Every time you come away you have got to be on your toes and giving everything you have got. I would say it's the strongest squad so far."