PHOENIX -- A little over a year ago, A's reliever Ryan Cook set foot in the Oakland clubhouse for the first time.

Fresh off a trade from Arizona, the powerful right-hander was in a strange new place, oblivious to what that moment would come to represent.

"I came into the clubhouse knowing virtually nobody," Cook said. "I could never, ever have imagined last year turning out the way it did -- as a team and individually."

Cook was dominant from the start in 2012, posting 21 consecutive scoreless appearances to open the season. He finished equally strong, by putting up zeroes in 22 of his final 23 trips to the mound.

The key now for Cook is to duplicate the effectiveness while avoiding complacency -- a common theme for many A's this spring. That shouldn't be hard for Cook, whose fiery demeanor on the hill would seem to leave complacency out of the equation.

"We're all competitors any time we take the mound," Cook said. "It was an amazing ride last year, but what happened last year is done. I'm coming into 2013 with the same expectations on myself as I've always had."

Last year Cook's role fluctuated throughout the course of the season. First, he was a dominant setup man. Then he was a dominant closer. Then, in late July, he ran into his first bit of adversity.

That's when Cook blew four saves in five attempts, before allowing two runs in the ninth against the Angels in a game he shakily closed out. The struggles prompted manager Bob Melvin to move Cook back into his original role, and the A's took off from there. With Cook setting up Grant Balfour, the Oakland relief corps cemented itself as one of the league's best.

"What we did last year just makes you more hungry," Cook said. "It makes you realize what it takes to play at that level every night. That little taste that we got of the playoffs gives you a driving force to do it again -- and go further."

A's catcher Derek Norris got plenty of work with Cook last season after he was called up from Triple-A Sacramento in June.

"I kept hearing about a guy that hadn't given up a run in his first whatever innings," Norris said. "I knew a guy like that has to have pretty good stuff to keep a zero ERA, and then when I got up there I saw what it was all about -- it was impressive."

Impressive enough that Norris even called Cook's stuff "hard-to-catch."

By the end of the season, the A's relievers had become renowned for their intense celebrations after big outs, but Norris said the "flex-mode yelling" was originally patented by Cook.

If there's one image of the 2012 version of Cook that stands out for Norris, it was those adrenaline-filled reactions after key outs, especially late in the season.

"How calm his personality is, and then he turns on the light switch when he steps on the rubber," Norris said. "He's real calm and goofy in the clubhouse, and then he goes into terminator mode."

Cook doesn't exactly call it terminator mode. But of all the things he learned last year, Cook said coming into games with the right mindset was the most important.

For a player who thrives in intense situations -- as he did during last September's American League West pennant race -- mentally recreating that intensity in every outing is the key.

"You never take anything for granted," Cook said. "I've still got to pitch well and perform. At the end of the day, the results are what matters."

Mechanically, there isn't much that Cook is looking to change this spring. Stuff-wise, he plans to keep it all the same.

Asked to describe that stuff, Norris used one word: "power."

"He's got real good movement and every time he throws, it's everything he's got," Norris said. "He's not a finesse pitcher by any means. He throws strikes, but it's full-tilt every time out."

Cook is looking to re-create that in 2013 for himself, for his team and for the Oakland fans, to whom he endeared himself awfully quickly.

Turns out, those fans had the same effect on him.

"We had such a close bond with the fans last year," Cook said. "Down the stretch, we really felt like we knew everyone in the stands and everyone knew us on a personal level. We feel like we owe that to them again, and we just need more of the same."

More of the same from Cook would have the A's and their fans feeling very secure in the late innings in 2013.