The Championship club are one point and one place above the relegation zone, conceding 64 league goals this term.
Defender Madl told BBC Radio London: "It's maybe because of (a lack of) concentration, not (a lack of) quality.
"If we change these small details and are a bit more concentrated then I think we will get out of there."
The 28-year-old Austrian, who made his debut in the 3-1 win at QPR in February, has impressed since his loan move from Sturm Graz.
But relegated-threatened Fulham have continued to struggle, winning just one of their eight matches since that derby victory, and defensive lapses have cost them valuable points.
"It's difficult to explain. We have a good team and some good defenders, but we make easy mistakes," Madl admitted.
"Sometimes we've played a very good 45 minutes and in the second half, especially in the last few games, it was not that good.
"We've had many penalties given against us and maybe the small details we don't do well, and it has cost us many points.
"We score many goals, but we concede too many. Just the small details we have to do better and, if we do that, we can win more games. We still have a good team and we still believe in us."
Madl's side face a crucial match on Saturday, when Milton Keynes Dons - the team immediately above them in the table - visit Craven Cottage.
"It's a massive game but we are well prepared and have enough confidence and quality in the team to win this game," he said.
Fulham must improve their concentration and work on "small details" to end the defensive errors that have blighted their season, says Michael Madl.