For one season, at least, the Twins were totally wrong. They didn't get middle-of-the-rotation production from him. They didn't get bottom-of-the-rotation production. Mostly, the team got very poor performance for what is agreed to be a lot of money.
What went wrong? There are some numbers and circumstances that tell the tale. First of all, Nolasco has always given up a lot of hits and hasn't been very good at stranding runners. The naysayers of the contract pointed that out from the beginning. Secondly, Nolasco had spent all his career in the National League, where, without a DH, it is thought to be easier for pitchers to put up good numbers.
The last two factors--health and luck-- may or may not be supported by numbers. Nolasco pitched with forearm tightness from spring training until he was disabled in early July. He pitched to an awful 5.90 ERA prior to going on the DL, and post All-Star game yielded a more representative 4.39 ERA.
Finally, Nolasco posted a 4.30 FIP, indicating that he suffered from bad luck and bad defense. In watching most of his starts, I would submit that he didn't get much help from his defence and that he suffered from a bunch of bloop hits and some bad hops. I also saw a lot of hard-hit balls with quite a few reaching the seats.
What does the future hold? First of all, while the first year was a disaster, Nolasco's body of work suggests he'll bounce back. He's been pretty dependable and reliable for a long time. No, he won't be traded in a salary dump and I sincerely doubt that he'll be exchanged for another "bad" contract. He'll get a chance to come back for the Twins. Secondly, I don't see him in the top of Twins rotation next year or for the duration of his contract. The Twins signed him 10 days short of his 31st birthday, and it is doubtful he'll ever perform better than he has in his better years ('10, '12 and '13) and not close to his best year in '08.
In looking at Ricky's season, I would classify eight starts as "good" or better, six as "meh" to average, and the remainder (13) qualify as poor. Certainly not good enough, but there were some decent outings. How much was health related? An open question. I think Nolasco has learned a bit about what he has to do to succeed and might minimize those poor starts. He showed a pretty good breaking ball to go with an OK fastball but he needs to mix his pitches effectively. Finally, the Twins need to improve their defense. Better defensive outfielders would likely disproportionately benefit this veteran hurler.
Better defense, better luck and better health will most likely lead to better results. I doubt he will ever be regarded as a good signing, but I also doubt he'll be viewed as a total failure going forward. The Twins should have gotten better production for over $12M per year, I think they'll get closer to it for the rest of his contract. But much like Joe Mauer, people will expect more than he'll produce.