Monk has found results hard to come by since replacing Michael Laudrup, picking up just two wins from 11 games, but the former defender has been impressed with the contribution of the 29-year-old midfielder.
The 35-year-old told the South Wales Evening Post: "Wayne has been one of our best performers since I took over.
"He is so consistent. He has always been a seven or eight [out of 10], even higher in some games.
"Some players can be brilliant one day and then rubbish the next, and that's frustrating. That consistency Wayne has shown is what you want."
Routledge has scored five times in 31 appearances for the Swans during the current campaign.