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OXNARD, Calif. (CBSDFW.COM) - Rolando McClain has a well-earned reputation for being enigmatic and even uncooperative. But he's also bright and introspective and clever, as he demonstrated at Thursday's opening of Cowboys training camp, when the gifted middle linebacker addressed his coming four-game suspension for violating the NFL's substance abuse policy.

"It's life; I ain't perfect," McClain said. "Nobody else is. I am working on perfecting my flaws and getting back and being healthy and doing my best to put it behind me.''

McClain's health is indeed another issue; he is starting camp on the physically unable to perform list because of offseason knee surgery.

"When I do I come back, I will try to improve the defense and build on the success they are having,'' said McClain, who said he doesn't have a specific timetable for returning to the practice field but that he is working both physically and mentally to prepare. "To miss a game and four games, it's going to be tough. I'm going to do my best to keep my mind in it. I know I will be working hard to stay ready for it. The toughest thing will be to keep my mind right.''

The Cowboys brought him back on a cheap one-year contract yet the former Raiders first-round pick -- with a career dotted with drug-test failures and early retirements -- says he feels appreciated by Dallas.

"The best thing about it was the warm welcome I got -- not only from Mr. (Jerry) Jones and the coaching staff but all of my teammates," McClain said. "I didn't know what the expectations were for me last year. But now that I see the ability that I have and not only that but the love and the passion I have for the game."

McClain said he has a vision of greatness for himself and fellow linebacker Sean Lee, who was in the middle last year before a season-ruining injury that caused Dallas to pull McClain out of retirement as his replacement.

"I always think highly of myself," McClain said. "Don't matter what you guys or anybody else expected of me. I have my own expectations for myself. At the end of the day, whatever the outcome is, as long as you can look yourself in the mirror and say, 'Hey, I gave 100 percent,' I can live with that. ... (pairing with Lee) I think about all of the time. Y'all will have to wait and see, but it will be fun."