You're using it as a factor as to why he could've played badly or as a reason to further commend him for playing well. I'm saying that this 'CL debut' thing (which it wasn't) isn't a reason to give extra praise or exclude him from criticism.
Qualifiers are a level below the nitty gritty of the group stages against the third best team in Germany. It was his 'full' debut for United/CL debut for them and he played very well. It was obvious how much more solid the team looked with him. He hasn't had a chance to play in easier games so it's too early to judge, when Cleverley is playing against the easier sides.