But that's my point: Vina del Mar, the tournament he lost to Zeballos, was his tournament he had played in 8 months, so he was rusty. When he got going, he was nigh unbeatable through the US Open, winning 10 of his next 12 tournaments, losing only to Novak at Monte-Carlo and that ill-fated loss to Steve Darcis at Wimbledon. No deal with the Devil, just Rafa at the top of his game. Elo supports the view that 2013 was Rafa at his very best. You could argue that 2010 was even better, but as far as his form on court, I think he was at his best in 2013.
The point being, let's see Rafa in his next tournament, and the tournament after, before pronouncing him cooked. He could be, but I'm not judging that based on his first tournament in 15 months. He's also probably being deliberately hesitant, to give himself a chance to jump on the moving train without tearing an arm off. The goal is being in his best possible form by Roland Garros, which is still 5+ weeks away. The last thing he wants to do is over-play at an ATP 500.
That said, I don't think any great player has been out that long and come back anywhere close to peak form, let alone at almost 38 years old. If he wins any tournament this year, it will be a remarkable achievement.