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04/01/2013 11:10 PM ET

Melvin keeps defending AL West champs grounded

OAKLAND -- The A's took the field in Oakland for the first time as defending American League West champions on Monday, with manager Bob Melvin urging them to put that title in their back pocket once play began with the Mariners.

"You have to put that away and don't think that just because you're the defending AL West champs that you just throw your glove out there and it's going to happen again," Melvin said. "We have to play with the same determination and fight and carry that momentum that we had last year into this year and know that nothing's given to you.

"You have to fight and prepare that much harder and have the same mindset, which is go out there and take something from somebody instead of expect to just get something."

The A's opened the 2013 campaign in front of a sold-out crowd that resembled the ones that showed up during last year's playoffs. Nearly an hour before first pitch, fans were chanting "Let's go Oakland!" and waving gold rally towels in the air.

They soon erupted in noise when A's players took the field.

"We garnered a lot of confidence from them last year, and I've said all along how much the fans meant to us," Melvin said. "We're lucky enough to be opening up at home. It's 161 and Opening Day. It's very exciting, everyone's a little more nervous, and it really does have a playoff feel to it."

Before the game, the A's paid tribute to the victims of the Sandy Hook shooting tragedy by joining with the fans for a moment of silence. All players across Major League Baseball wore a Sandy Hook memorial patch on Monday.

Worth noting

• Yoenis Cespedes is the A's 14th different Opening Day starter in left field in as many years.

• The average age on the A's Opening Day roster is 28.03 -- youngest in the AL and second youngest in the Majors to Atlanta (27.79).

• The A's have two rookies on their Opening Day roster (Nate Freiman, Dan Straily) after having seven last year.

Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.