Ki was loaned out to Sunderland on a year-long deal last summer after falling out of favour under Michael Laudrup, who decided not to exercise a recall option in January.
Monk has since replaced Laudrup at the Swansea helm and has made it clear that Ki remains a vital part of his plans for the future.
"Ki is a quality player. You can see the potential he has with what he has delivered for Sunderland this season," Monk said in the South Wales Evening Post.
"He has put in some great performances up there and he's been scoring goals, which has not been great for us.
"In a way it's good to see, but in another way you don't want to see it.
"I think Ki could potentially be a great player for Swansea, but of course we will have to see how he feels at the end of the season.
"I don't know if other clubs will be interested in him come the summer - all that will come out.
"But he is a Swansea player and he is the type you want at the club.
"We need to let players like Ki know how important they are going forward and I think he is.
"He might not have suited one manager, but it doesn't mean he won't suit the next manager. For me, I think he is a very good player who could play a key role for Swansea."
Sunderland manager Gus Poyet has previously admitted that he would love to keep Ki at the Stadium of Light beyond the end of the season, while the player has yet to reveal where he sees his future.
Ki has just one year remaining on his Swansea contract, having made the move from Celtic in 2012.