The 28-year-old had been sidelined with a chronic bowel problem, but played the full 90 minutes of United's 2-1 League Cup victory over Newcastle United last Tuesday and also made an appearance off the bench in his side's opening Champions League tie with Galatasaray.
Fletcher, who is still the captain of his national side, is getting back to full fitness but is expected to be named in Craig Levein's squad for the forthcoming World Cup qualifiers with Wales and Belgium.
"Obviously it's the manager's decision to pick me and he'll be looking at how much game time I've had for United," the Scot told The Sunday Mail.
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"But I'm desperate to be involved. I was desperate to be involved in the Serbia and Macedonia games as well but it was just a little bit too early for me.
"I came up for the Serbia clash but United had a reserve game on Tuesday at the same time as the Macedonia match.
"I felt it would be better for me to get it under my belt.
"I wanted to be at Hampden, though. As captain of the squad you want to be there for the players, for the manager - you want to play your part."
Scotland got their World Cup qualifying campaign underway with two disappointing draws to Serbia and Macedonia but Fletcher believes there is more to come from the Tartan Army.
"Everyone agrees that two points wasn't good enough - but not to the level of criticism we got. We should have had more, definitely from the first game," he added.
"I honestly thought it was a good performance. Serbia are a good side and beat Wales 6-1.
"I knew it would be tough but we approached the match the right way. Maybe four points would have been a good return but it's by no-means over.
"We're capable of getting results in the next two games, without doubt, and we'll be looking to do that. We're behind the manager and what he's doing. We respect him and are prepared."