Re: Is it possible Nadal will never return to his previous level?
Even in his first week back, Nadal is already almost at 'the previous level' now. Even if Nadal was in Championship form it is likely Del Potro would have taken him to a tie-breaker. So the first set was close to that form. Mentally his concentration isn't back yet, he pointed that out after the match, and often when concentration is down you do give your serve away early in the 2nd set after a tight 1st set and struggle to get back into the zone.
Based on the Del Potro match, Nadal is far ahead of the schedule I was expecting, I expected he'd take until the end of Cincy to reach this kind of form or at the latest maybe round 1 or 2 of the US Open. He may need a 4 or 5 setter to feel himself again mentally, so hopefully he gets that early in the US Open in case he has to play 4/5 sets in the Semis or Final.
Its really all mental now for Nadal, his movement is fine.