The Scot featured in victories over Olympiacos and West Ham United.
"The team don't like what's happening this season," Fletcher told the Sunday Times.
"The biggest thing, and I felt it, there's been no real celebration since Olympiakos. No, 'Wow, we're back'. There's a lot of work to do. At the end of the game it was, 'Listen lads, we've done nothing'.
"We're in the Champions League but our league position doesn't give us any right to make out we're back."