After clawing their way out of the bottom three last week, the Latics are back in trouble following a 3-2 home defeat by Sunderland. Martinez blamed the setback on the knee injury Ivan Ramis suffered at Fulham last week, which led to a defensive frailty, with Steven Fletcher moving onto 10 goals for the season with an impressive first-half double.
But Martinez is adamant that, after eight years in the top flight, no-one at Wigan is resting on their laurels, and he said: "We never take anything for granted. If we had done that we would never have had eight seasons at this level."
He added:: "We weren't good enough defensively for 30 minutes. We need to rectify that. Ivan Ramis' injury last week cost us points. That is something I need to correct."
Sunderland's response to conceding an early own goal from David Vaughan was impressive. With new-boy Alfred N'Diaye an imposing midfield presence on his first start, the visitors levelled through Craig Gardner's penalty - Sunderland's first in 34 matches - before Fletcher hit Wigan with a superb one-two.
The Scot clearly enjoys facing the Lancashire outfit as he has now scored six times against them in seven appearances. His first owed much to his lightning reactions after Ali Al Habsi had turned away his header, with the second an instinctive curling strike from Adam Johnson's lay-off.
"Fletcher was fantastic," said Sunderland boss Martin O'Neill. "It was not just his goals but also his whole centre forward play. We took great heart from his performance."
At that stage Wigan were inept and staring down the barrel of a big defeat, but the half-time introduction of midfielder Roger Espinoza triggered an immediate improvement and fellow new-boy Angelo Henriquez made his mark when he scored his first goal for Wigan when he nodded home Shaun Maloney's far-post cross 11 minutes from time.
"I was pleased that they didn't seem like new players," said Martinez. "They looked like they knew exactly what they were doing.
"Roger is someone with great energy, which he compliments with a real style in possession. Angelo is a goalscorer and to score a goal on your Premier League debut is a great boost for his career."