ARLINGTON -- Guillermo Moscoso carries a little pink backpack with light blue straps when he goes to the bullpen. As funny as it sounds, he enjoys these initiation procedures for rookies.

"We know we're going to carry the pink bag when we come up," Moscoso said. "It's filled with water, pills, Red Bulls, everything we need out in the bullpen. That's my job right now."

Moscoso hopes to be around for another month or two when his Rangers teammates will give him a costume to wear while on road trips.

They might not have the chance to do so. Starting pitcher Vicente Padilla is scheduled to come off the disabled list and start Tuesday against the Yankees. That means someone will have to be moved off the 25-man roster.

Moscoso was called up from Double-A Frisco before the second game of Friday's doubleheader against the Athletics. He made his Major League debut in Saturday's 14-1 Rangers victory over the A's and pitched a scoreless ninth inning to close the game.

"I thought he did a good job," Rangers manager Ron Washington said. "He made a great pitch on the double play and didn't seem nervous. He came as advertised: He threw strikes."

Moscoso allowed a single to lead off the inning but responded with a strikeout. He gave up another single, but got Ryan Cunningham to ground into a double play to end the game. Moscoso enjoyed his inning of work.

"It felt great," he said. "It's something you dream of forever. I got the opportunity and I got focused on that. I did the best I could do.

"That was one of my best moments in baseball."

You can excuse him for not saying that was his best moment. Moscoso threw a perfect game with the Oneonta Tigers in the New York-Penn League on July 15, 2007. It was the second perfect game in the history of the league.

"I was thinking about the perfect game in the seventh," he said. "I was getting nervous in the eighth."

The Rangers acquired Moscoso when they dealt catcher Gerald Laird to the Tigers on Dec. 8 this offseason. Moscoso had been 3-1 with a 4.50 ERA in nine games (seven starts) and limited opponents to a .246 average while with Frisco. He opened the season with two relief appearances before moving to the rotation full time.

The Rangers also acquired pitcher Carlos Melo in the Laird trade.