Dortmund remain two points adrift at the foot of the table after crashing to a 1-0 defeat at home to 10-man Augsburg on Wednesday.
Hummels and vice-captain Roman Weidenfeller spoke to frustrated supporters post-match following a fifth league match without success.
No one could have predicted Dortmund's demise, having seen Jurgen Klopp's men finish in the top two in the past four Bundesliga campaigns.
However, the danger of being relegated to Germany's second tier for the first time since 1971-72 is becoming an increasing concern.
"We're always chasing games after going behind," Hummels said after Wednesday's defeat. "What's missing is us taking the lead so that we can then sit back and play on the counter.
"We're all aware we've got to fight in these next 15 games.
"Playing attractive football will just be a bonus - we're still expected to play great football.
"Ninety-eight per cent of this is about the fight. The other two needs to be about loosening up so that we start making the right decisions in the final third."
Only two points separate Borussia Monchengladbach, Augsburg, Bayer Leverkusen and Schalke ahead of this weekend's fixtures.
Gladbach occupy third position with 33 points, two clear of sixth-placed Schalke, leading into Friday's showdown at Veltins-Arena in Gelsenkirchen.
Elsewhere, youth team coach Pal Dardai will take charge of second-bottom Hertha Berlin as they travel to Mainz after Jos Luhukay was sacked following Wednesday's loss to Leverkusen.
