Both sides have 14 points from 14 games ahead of Monday night's meeting on Tyneside, where Newcastle have lost their two previous Premier League games.
But Martinez said: "We need to remember that Newcastle are capable of reaching really good heights of performance and results.
"Remember what they achieved last season in finishing fifth was a phenomenal achievement, and it's going to be a very difficult game.
"Sometimes in this league you can get in a run of bad results but we're going to expect Newcastle to perform very well and make it difficult."
Wigan will wear red for the first time since their Division Two title-winning campaign of 2003.
Martinez said: "We have some very happy memories of playing in red kits and I feel it's important that you associate iconic kits with success."