What can I do if I was wrongfully terminated and what is my first step?

I was a great performing manager with a solid work history. I was terminated in January of 2013. I'm not sure if the statute of limitations is over or not however I thought I would ask. I never attempted to file a case because I spoke to previous attorneys that said my case would be difficult to prove. Here is what happened. I was employed with this company for approx a year when I severed my Achilles tendon. As a result I was on short term disability and FMLA for 11 weeks. Upon my return, my previous team had been disbanded and absorbed by other teams in the company. I was given the worst performers within the company to manage and told I had to improve their performance. These were performers that NO previous managers were able to improve. Five other managers had this task of trying to improve this team and they ALL failed. One manager after another they failed miserably. After the 5 other managers failed, they were all given different teams to manage (great performing teams). The company policy was after 3 months of low performance, you would be put on a performance action plan. At the end of the 3 months, you would be terminated if the team’s performance did not improve. The other managers were all transferred to performing teams after the second month to avoid them being placed on a performance plan. I in turn was terminated. If all of the previous managers failed as well as myself, why was I the only one terminated? I had good attendance and a previous great track record.