Hmm yeah, that's something he can improve on. Maybe he feels sometimes he doesn't have the speed joining the counter from deep when he's behind others.
Depends also on the tactical set up he is playing tbf.
I expect this season will be more about learning than actually impressing every game for him (when he plays).
Last season he had the 'advantage' that the team was lacking any kind of creativity and flair. When he played, creating was his main goal. If a pass failed, he'd try it again the next minute because the other players and the manager knew he was the one they were looking for to create. He was the man that was capable to provide something they couldn't. In short, he was Utd's main attacking player.
Now it's different. Other, more high-profile and maybe better, players have come in/back and have become the main men. When Januzaj gets his chance, he's just one of the players now, meaning the defensive and tactical part of his game has become a lot more important than it was last season. During the first few games this season he had to adapt to that, it's something that will take time but will be very important for his career.
For his type of player, decision making is key. I'm sure Giggs and Van Gaal will improve that.
The 30 mins today and his cameo as a central midfielder emphasized that. Playing in a different role or with other instructions (Belgium's manager wants defensive stability) he didn't yet find the right balance.
Playing as a central midfielder that time, most of his passes were safe, even when we needed the 'killer-pass'. It's all part of adapting to new responsibilities and roles. In the end it will help him and he'll be fantastic, but it might limit his playing time this season, knowing the competition.