For others, even if they don't have much success, it's still beneficial to face the stiffer competition. And getting to shadow established stars can give the prospects a better idea about how best to approach their work.
"It can be intimidating for the younger guys," Lieppman said. "But take someone like [infielder and 2004 draftee] Kevin Melillo. He gets to take ground balls behind Mark Ellis and see what kind of technique he uses. He has the opportunity to see what a Gold Glover -- or should-be Gold Glover -- does and what makes him successful.
"It's just great for our young guys to see how guys like that work, because a lot of them -- Nick Swisher was one of them -- start out thinking they have to do more and work harder. Swish used to go overboard. But being in the big-league camp hopefully shows them that it's more about the kind of work you're doing. It's the quality that counts."
On the move: Like Buck, first baseman Daric Barton is expected to reach the Majors at some point this season, and he's been showing everyone why.
"He's been very consistent with the quality of his at-bats," Lieppman said of Barton, who went 2-for-6 with two RBIs in the first three games. "I think people are realizing how good he really is, and he's understanding what kind of player he can be, too. He's had some great at-bats."
Lieppman also is pleased with Barton's mental development, which was expedited this offseason when he played for Azucareros del Este of the Dominican Winter League.
"It wasn't a very good team, but Daric kind of rose to the occasion and really became a leader down there; he became a catalyst and really turned that team around," Lieppman said. "A lot of players go down there, and come Christmastime, they go home and get ready for Spring Training. Daric did that, but they called him and asked him to come back for the playoffs, and they usually only do that with their guys who have been in the big leagues.
"I think that says a lot about a 21-year-old kid."
On the mend: Outfielder Javier Herrera, also 21, missed last season after having Tommy John surgery on his right elbow in April and is in big-league camp, but he hasn't played in any Cactus League games. Lieppman said Herrera's arm, once touted as the best in the organization, is at about 80 percent.
"It's coming together for him," Lieppman said. "He's been looking good in batting practice, real strong, real sharp, and I think they might throw him out there pretty soon."
They're No. 1: Shortstop Cliff Pennington, Oakland's top pick in 2005, isn't in big-league camp, but he was among the players reporting early to Papago this spring. He had hamstring problems throughout the 2006 season.
"It affected him from the very beginning, so it was kind of a lost year for him," Lieppman said. "Then he hurt his hamstring again in a pickup football game around Thanksgiving. But he's healthy now, and if he's healthy, he should have a solid year.
Pennington batted .206 with a .302 on-base percentage in 46 games for Class A Stockton last season, and he'll probably return to Stockton to open the 2007 campaign.
"Guys who didn't have a lot of success the previous year, you want them to start at a level that'll help them gain some confidence," Lieppman said. "When he gets hot, you move him up."
Class of '06: Righty Trevor Cahill, a second-round pick last June, pitched in four games in the Arizona Rookie League and was limited by biceps soreness in the fall Instructional League, but Lieppman said he's received good reports on Cahill's winter.
"There's a league down in Southern California that's run by one of our scouts, and from what I hear, Trevor was very impressive in that," Lieppman said. "He's in good shape, and he's had a good attitude."
What they're saying: "It's pretty exciting to see guys like Buck and Barton doing so well. They're going to be a big part of this team's future." -- A's manager Bob Geren