Melbourne Heart coach John Aloisi has admitted concerns with his A-League side's inability to rise to challenging situations.After a disappointing 2-0 loss to Adelaide United at AAMI Park on Monday night when a top six spot beckoned, instead the Heart face a mountain to climb to reach the playoffs.They are now second-bottom with three matches left, and face table-topping Western Sydney Wanderers this weekend needing all three points to re-ignite their finals push.Aloisi admits his side is showing a disturbing lack of urgency in challenging on-field situations.Until Monday night, the problem had been in away matches.But after going a goal down to a soft Dario Vidosic penalty, the cheese slipped off the Heart's cracker entirely in the second half.Bereft of ideas and inspiration as Adelaide controlled the match, the Heart never looked likely to fight back into the game."We haven't won coming from behind yet this season. When things are going well, and they have been at home, we're probably one of the best teams to watch," Aloisi admitted."When we went a goal down, the team's heads dropped too easily."That was disappointing because that's happened quite a few times this year."Making the problem more puzzling is that the Heart remain the A-League's best first half team, and would be topping the table were matches played over the just the first 45 minutes.Aloisi said he must shoulder full responsibility for the issue, saying it was up to him to find a way for the team to fight back into matches when behind.Aloisi left out defender Patrick Gerhardt and midfielder Jonatan Germano for Monday night's match after the side's tough recent schedule, but expects the pair to return for Saturday's critical clash with the Wanderers.