Maybe by best cornerback in NFL, he meant best pro-creator of children in the NFL?

I can see how you can get the two confused. Here is what Cro had to say via Pro Football Talk.

“I have said that I’m the second-best corner in the NFL,” Cromartie said. “I’m not backing off what I said. I don’t care what anyone else believe. . . . It’s my confidence in myself. I know what I’m capable of when I’m at the top of my game.”

Cro is a good corner, at times he has shown flashes of being excellent DB and it is good he has confidence in himself, but he isn’t the best corner in the NFL.

But, he is going to have to play like it if the Jets have any chance to prosper this season.