Dyer, who joined the club in 2009, has slipped out of the first-team fold in recent weeks, but Monk insists the winger has nothing to worry about.
"These are very difficult decisions for me," said Monk.
"Nathan had a fantastic start to the season, then he had a little dip and then he came back a bit. He has probably been a bit more inconsistent, but he has still contributed fantastically to the team.
"There are no problems whatsoever with Nathan. He is one who does deserve to be in the match-day squads, but unfortunately with the way things are sometimes, that isn't always possible.
"I have known him since he was 14, I know him better than probably anyone else in the squad. I have watched his career.
"But there are moments within seasons when you miss out. It is not just Nathan, there are others, too, who have missed out. Look at Tom [Carroll] and Jay [Fulton]. They were fantastic at Southampton and it was a tough decision to change it after that.
"It depends who we are playing, how the players have trained. Jeff is different from Wayne and Nathan, Wayne is different from Nathan. Then we have Mo Barrow coming through; they are all different types who can contribute different things."
In Dyer's absence, Swansea recorded wins over Manchester United and Burnley, before losing 3-2 at Tottenham last time out.
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