The Wigan defender has not featured at first-team level since recovering from a hip operation in the summer but was drafted in by Craig Levein for the forthcoming double-header against the Czech Republic and Spain.
With Lee McCulloch suspended for the first game in Prague on Friday night and Paul Hartley out injured, Levein could revert Caldwell back to the holding midfield position he occasionally played at Celtic.
However, the defender is happy to take on any role, regardless of obvious questions surrounding his match fitness.
"You will never be match fit unless you play matches and when you come back from injury, there is always going to be a first game," Caldwell said.
"You are never going to be 100% right so whenever that game comes, it probably is going to be gamble.
"But you have to take that some time and if it's Friday night or the following Tuesday, I have said to the manager I am ready for that challenge."
The former Hibernian defender continued: "I was surprised to be in the squad.
"But it was a boost for me to get back involved so soon.
"I am just happy to be back, I have been out for a long time.
"But I have been training for a long time and I am fit enough to play.
"I haven't played enough football in terms of 90 minutes.
"I have played 45 minutes at the training ground then I had a reserve game against West Ham where I played 65 minutes so 90 minutes is the next step.
"I am ready to play and do what the manager asks me to, but that will be his decision."
Scotland have taken four points from their first two games against Lithuania and Liechtenstein and probably need at least a draw out of the visit to Prague to keep qualification hopes on track.
Levein, though, was keeping his cards close to his chest as to the possible utilisation of Caldwell but conceded that he will not be used in both games.
"I don't think there is any chance of him playing the two games," the former Hearts and Dundee United boss said.
"He has been out for a long time but is way ahead of schedule with his recovery.
"I wanted him around the place because he is a great character and very professional and I think he will help the rest of the squad.
"I think he can contribute but until I see him in training this week I couldn't tell you how much."
Caldwell allowed himself to fast-forward to the glamour game against Spain at Hampden on Tuesday week but insists the match against the Czech Republic, who are realistically vying with Lithuania and Scotland for second spot and a play-off place, is the more important.
"I think the Spain game is one we can look forward to," he said.
"It is not often the world champions come to Hampden and we can go into the game with no fear and just go and play them.
"When you look back over recent years, even when we have not qualified, we have beaten Holland, we have drawn with Germany and beaten France so we do have a good record against bigger teams but I think Spain is an altogether different challenge.
"They are probably one of the best national teams there has been for a long time.
"Both are big games but Friday night in terms of qualifying is probably the bigger game.
"If we can go there and win then it will be a massive boost for us and knock them back."