By Mychael Urban / MLB.com

Carlos Pena hasn't homered or driven in a run this month.

The players summoned from Sacramento are second baseman Esteban German, outfielder Adam Piatt and first baseman Larry Sutton.

The biggest surprise is the demotion of Peña, who was named the American League's Rookie of the Month for April after hitting .274 with seven home runs and 16 RBIs. He hasn't homered or driven in a run in May, and a 4-for-40 slide has dropped his average to .218.

Contacted via cell phone prior to the club's announcement, Peña said he hadn't yet heard anything from the club and expected to be in Oakland for the opener of the A's three-game series against the Baltimore Orioles.

"If that's what happens, it happens," Peña said. "I can't worry about what this person thinks of me or that person. I cultivate my own garden. I know in my heart that I'm not a Triple-A player. I'm a big-league player. But if I have to prove that -- again -- at Triple-A, that is what I will do."

Menechino got off to a hot start as well, but his average is down to .210 with three homers and 14 RBIs. Tam has been ineffective all year, compiling a 6.52 ERA (17 earned runs, 19 1/3 innings) over 19 appearances.

German, a Dominican Republic native who missed most of Spring Training with visa problems, is one of Oakland's top prospects among position players. He's hitting .277 with four doubles, a triple and nine stolen bases in 12 attempts in 37 games for the River Cats and will be making his Major League debut with Oakland.

Sutton, a 32-year-old left-handed hitting first baseman, was batting .310 with four home runs, 14 doubles and a team-high 26 RBI in 41 games with the River Cats. He was tied for second in the Pacific Coast League in doubles and ranked fourth with a .443 on-base percentage. He appeared in 181 games in the Majors with Kansas City from 1997-99 and 56 games with St. Louis from 2000-01.

Piatt, the 1999 Topps Minor League Player of the Year, is hitting .282 with five homers and 24 RBIs at Sacramento. He hit .290 is 60 games with Oakland in 2000 and .211 in 36 games last season before a bout with meningitis forced him to miss most of the rest of the year. He also missed time this spring with a rib-cage injury.

The moves came a day after general manager Billy Beane met with Howe and his staff on Oakland's off day, and more moves might be coming. A source within the team has confirmed that the A's are actively looking to unload one of the three left-handers -- Mike Magnante ( 7.94 ERA), Mike Venafro (2.45) or Mike Holtz (6.00) -- from their beleaguered bullpen.

Mychael Urban covers the Oakland A's for MLB.com and can be reached at murban@oaklandathletics.com. This story was not subject to approval by Major League Baseball or its clubs.