"The equaliser is what disappoints me," Martinez told BBC Sport. "It is not a free kick in the first place.
"When you are at the bottom of the table, it seems you attract the ball to the back of your net sometimes, but those are the small margins that sometimes affect the results.
"But I couldn't be happier and prouder. We need to perform in the same manner, if we perform as we did today then we will be okay."
The draw means that Wigan are now two points adrift of safety with four games left to play.