Following Friday's 2-1 defeat by Wales at Hampden Park, Scotland currently sit bottom of their qualifying group without a win and with just two points from five games.
Rhodes admitted: "It's going to be a real tough ask now. Hopefully we can go to Serbia and get the win and the three points that we are looking for.
"We're not kidding ourselves, it's going to be tough to go out there. But we have to stay positive and keep working hard. Hopefully with that attitude we will come away with the win."
The Blackburn striker is looking for his first competitive international start in the absence of the injured Steven Fletcher and said: "I'll give it my best shot. If I'm called upon I'll be ready. I approach every game in the right manner and this one will be no different. I'll try my best and that's all I can do.
"I don't know what the manager's thoughts are for the Serbia match. That's his call to make. I've been doing well for my club and if called upon for my country I would do my very best. That's all I can do."
Rhodes has 23 goals so far this season in a struggling Blackburn side but was only called upon by Gordon Strachen with five minutes to go in Friday's defeat to Wales.
"I'm disappointed and as a group we're disappointed," he added. "Wales had more possession but we created the better chances and were winning 1-0 - life was good.
"It's such a shame we conceded a penalty because that sending off turned the game. But we need to pick ourselves up and ensure we're ready to go again against Serbia. That is the focus now."