The defending champions are third in the table before Saturday's home game against Union Berlin, who have beaten top six clubs Borussia Dortmund and Freiburg in recent weeks. The Bavarian giants are hunting a first win in three league games following a shock home defeat to Hoffenheim and a 2-2 draw at Augsburg, conceding two goals in each of their last five games in all competitions. Kovac was also dealt a double injury blow in the last week with centre-backs Niklas Suele and Lucas Hernandez sidelined for the forseeable future. Kovac still expects to name a "powerful team" against Union with Jerome Boateng and Benjamin Pavard likely to replace Suele and Hernandez. "We aren't doing well defensively at the moment," admitted Kovac on Friday while also criticising media speculation over his job as "disrespectful". "We are making too many individual mistakes, you have to win the one-on-one challenges. "We have a few injuries, some are severe cases, but we're not crying about it -- that doesn't help -- we're making the best of it and getting on with it." The German media has speculated that both Kovac and Borussia Dortmund head coach Lucien Favre are under pressure for their jobs. Magazine Sport Bild claim RB Leipzig boss Ralf Rangnick could replace Kovac while Jose Mourinho would step in if Favre is fired. "We're only eight games into the (league) season, so that (the discussion about coaches) indicates a tendency, which is not good," said Kovac. "You can't question everything when you lose one game. "We're talking about respect and it doesn't have much to do with respect when you go straight for the coaches. "Dortmund is fourth (in the table), like us on 15 points. And suddenly everything is bad. "Names are traded, I don't understand that," Kovac added with Favre also saying Friday he is "not okay" with the rumours. Kovac hinted that the team's situation provides a chance for not only Boateng, but also Thomas Mueller, linked to Inter Milan and Manchester United since admitting he is unhappy with starting just five games this season. Mueller, 30, made a rare start in Tuesday's 3-2 Champions League win at Olympiakos and created two goals for Robert Lewandowski. "You need a bit of luck in life, unfortunately we have two long-term injuries, now we have to make it clear to those who play that they are important," said Kovac.  He expects a tough game against Union, who shocked Freiburg in Berlin last weekend. "Our task is to win the game and become league leaders," said Kovac. "You can see the stability in Union's game, they are good defensively and the answer is simple: don't give the ball away. "We have to stop giving possession away cheaply, then it will be easier to dominate. We may have to be patient."