Having held their own for much of the Premier League encounter at Eastlands in March, the Latics had Gary Caldwell sent off before a quickfire hat-trick from Carlos Tevez in the space of a little over 10 minutes condemned them to a 3-0 defeat.
Tevez's third goal was particularly impressive and Martinez feels City are always capable of producing a piece of trickery out of nowhere.
"In the game away from home we looked well in control in the first half and the sending-off clearly changed things," Martinez said.
"Then you saw a piece of magic from Carlos Tevez and he gave the scoreline a look that did not reflect the performance.
"That is what we are facing on Sunday - a group of individuals with a little bit of magic or a trick, and they can really hurt and punish you. We need to be ready for that."
With regard to his own team, Martinez believes Wigan are showing signs of progress this season earlier than might be expected.
After being thrashed at home 4-0 by Blackpool and 6-0 by Chelsea in their opening two games, Latics have steadied the ship in the last few weeks, pulling off a surprise 1-0 win at Tottenham before Saturday's 1-1 draw with Sunderland at the DW Stadium.
Martinez had four summer signings in his starting line-up against the Wearsiders with transfer deadline day arrivals Franco Di Santo and Tom Cleverley coming off the bench, and the manager feels his new-look group of players is already working well together.
"We are starting to show signs that we have no right to show yet because it is early on in the season," Martinez said.
"We are a real team and there is that feeling about every single performance.
"If we get that, we are going to get a lot of consistency and that is the biggest thing that we have had to solve.
"There are clear, good signs that we are progressing and getting stronger game by game, and that is where the excitement is."
One new recruit who endured a frustrating afternoon against Sunderland was striker Mauro Boselli, who missed a gilt-edged chance and was substituted soon after.
The Argentinian, signed from Estudiantes in June, is yet to find the net for Wigan in four league starts and a Carling Cup tie at Hartlepool, but Martinez is confident Boselli will rediscover his touch in front of goal before long.
"He will come good, and he has been good in many aspects and many areas," Martinez said.
"Mauro, like any other player, needs a bit of a settling-in period because the Premier League is completely different to any other league in world football.
"He is a proven goalscorer with a fantastic talent and we will get to enjoy his football at Wigan Athletic very, very soon."