This is a Performance vs Q question. I take the Q as potential. Its performance that decides and not just goals look at ratings, assists etc.

If you have the opportunity to do so bring the new guy on as sub with more than 20 mins to go (to get a rating) and see if he performs - if he doesn't, ordinarily I'd say sell him off and try again with another but that's not so easy now you let him gain 7th star.