Monk, who replaced the sacked Michael Laudrup in February, has won one match in charge - a 3-0 success against Cardiff City - but Martinez feels that it would be unwise to judge him solely on results.
"I have been very impressed with Garry Monk and it would be a big mistake to try to assess his time just by the results," Martinez told the South Wales Evening Post.
"Some of the performances have been impressive, especially the two games against Napoli in the Europa League where he brought a mature performance from the players.
"I don't think there is a big difference or something huge lacking. I have been very impressed with the way he has handled the demands of a short period of time with so many games."
Everton welcome the Swans to Goodison Park this afternoon.