He really is deluded in the extreme. Does he think he had the right to see out a 6 year contract, regardless of how he performed? He had an entire competitive season, and failed miserably. He makes it sound like he was sacked without reason after a month or something.
Also, imagine reading that as a Sunderland fan. "That is where I should be working, and my level is that." In other words, you're beneath me. It's not enough that he's already described the incredible "rebuilding job" he's got on his hands, but now he's spouting off about how he deserves to be at a bigger club. Imagine getting together with a girl, then spending the first date banging on about your ex.
"Well, I used to go out with a stunner, but she packed me in very unfairly I thought. She should have given me more time to prove I have a bigger dick, but I still believe that's the level of girls I should be attracting. In the mean time, you'll do of course, but I've got a tough job on my hands to get you up to her level, or even the level of your friends."