6 perhaps, maybe even 5, as missing a penalty is not great. Would have depended on the scoreline, though, and how costly the miss was.
But what kind of thing is that to say? It's like saying that if Kane hadn't scored any of the 29 goals he has scored this season, he would have had a poor season. Or that if Ronaldo hadn't scored as many goals as he scores, he wouldn't have been so highly rated. Or that if Hugo Lloris was making bad mistakes on a regular basis rather than world class saves, he would have been a pretty poor goalkeeper.
Obviously, if someone did a poor job rather than a good job, he would be less highly rated. But you have to rate someone by what they do, not by how you would have rated them if they hadn't done what they did. You can't say that someone would have been a pretty rubbish player, if you only take away all the good things he does. It's a bizarre argument.