For the German national team, it is important not to just win the game, but to make it as big as possible. Otherwise, they may lose the first place in the group. For example, if the Germans win against Northern Ireland with the score 1:0, and the Poles beat the national team of Ukraine 3:1, then Poland will rise to first place in the group, while Germany will slip to the second. In this scenario, Germany are likely to meet Spain as early as the quarterfinals. It’s not the thing you will want at this stage.
In fact, the German team has not even yet secured promotion to the playoffs. Therefore, Joachim Löw won’t rotate too much. For Northern Ireland, the goal difference is important, as well. If they lose 0:4, they will be below Albania that also finished third. But a 0:3 defeat won’t. So, if Northern Ireland will won’t rush forward even if they concede a goal.
I think that Germany will win on -1 handicap. The difference in class is enormous, and Thomas Müller is set to score his first goal at the tournament.