1. Travis Buck, OF
Unfortunately, Buck has been hampered by injuries for much of the season. He is currently on the 15-day disabled list and he has appeared in only 54 of the team's 80 games. Buck has made himself into one of the A's most important offensive players and the team's second-half chances will weigh heavily on how much Buck will be able to play. He is certainly on his way towards fulfilling the promise we saw in him when he was named the A's top prospect entering this season.
2. Javier Herrera, OF
At times this season, Herrera has flashed all of the tools that have made him a highly touted prospect for the past three years. He has wowed on occasion in the outfield with his throws and with his range, but he has also made a number of ill-advised plays out in center. Herrera has stolen 11 bases, but he has been caught six times. He has nine homeruns on the season, but he has a 59:19 K:BB ratio, something that is indicative of his tendency to over-swing in an effort to hit a homer in every at-bat. In fact, oftentimes Herrera appears to be trying to make-up for missing an entire season with one swing of the bat. There is no question that Herrera is a big talent, but, now at age 22, he'll need to start finding some consistency and start playing defense with an eye to the situation rather than the spectacular play.
3. Daric Barton, 1B
Barton has shown the ability to adjust to what pitchers are trying to do to him. His defense at first base continues to improve, although he still has more work to do in that area. He spent some time at third base earlier in the season, but he fared poorly there and looks much better suited to be a first baseman in the major leagues. When Dan Johnson was struggling in June, the calls for Barton's promotion to the majors grew louder. With Johnson hitting well again for the A's, those calls have cooled a bit. Still, if Barton continues to hit the way he has since May 1, the A's will have to find a way to get his bat into the line-up. Whatever luster he lost as a prospect last season when he was hurt, he has regained that luster and then some.
4. Kurt Suzuki, C
Interestingly, Suzuki was promoted to Oakland despite struggling in May to the tune of a 688 OPS. He had hit fairly well in April, batting .280 with a .364 OBP and was nine for his last 24 at the time of his promotion. Still, his promotion had more to do with Jason Kendall's offensive struggles and the desire of the team to move Adam Melhuse than it did with Suzuki's raw numbers. The A's have always liked Suzuki's work ethic and his willingness to learn and felt that he would learn more working with Kendall in Oakland than he would in Sacramento. Defensively, Suzuki has improved every year that he has been in the minors, but he is continuing to work on his receiving skills and on his game-calling. As a hitter, Suzuki has a solid opposite-field approach that should allow him to hit for good average in the major leagues. He has already shown in his brief major league tenure that he will burn a team that tries to go inside on him and he will go the other way if pitchers work him outside. If Suzuki continues to improve defensively under the watchful eye of the A's coaching staff, he should be first in-line to be the A's regular catcher next season.
5. Matt Sulentic, OF
Sulentic is still very young, so his struggles at the start of this season are not an insurmountable obstacle for him. However, they are a cause for some concern. Sulentic isn't a big guy (5'10'') and even though he is solidly built, it isn't clear that he will develop enough power to play a corner outfield position down the road. He has shown a little more pop in his bat since arriving in Vancouver, but he didn't get much behind the ball while in Kane County. The A's toyed with the idea of moving Sulentic into the infield last off-season, but, for now, he remains in the outfield. It will be very important for Sulentic to finish the season on a high note in Vancouver. If he finishes strongly and has a good fall instructional league and spring training, the A's could push him up to High-A Stockton at the start of next season. However, if his struggles extend into his time in Vancouver and through the fall and spring, it will be difficult for the A's to keep him on a fast track.
6. Kevin Melillo, 2B
Melillo has always projected as an above-average offensive second baseman and he has continued to display those tendencies this season. He will likely never have more than average range in the field, but he has gotten better at making the routine play and turning double-plays over the past two years. On a team without Mark Ellis, Melillo would possibly be in the major leagues right now. However, the A's love what Ellis brings on defense and Ellis has had a solid offensive season, as well. Melillo has not seen significant playing time anywhere but second base during his minor league career, meaning that he is effectively stuck behind Ellis on the A's depth chart. Oakland added Melillo to the 40-man roster when he was recalled to Oakland for a weekend series against the Mets in June and he will continue to be in the mix with Donnie Murphy and J.J. Furmaniak to be recalled if the A's need a position player. He also is a likely candidate for a September call-up. Ellis is a free agent after the 2009 season, so the A's will need to make a decision about whether they see Melillo as their future second baseman fairly soon. If the A's decide that Ellis is going to be their guy past 2009, Melillo could be trade-bait for a team looking for second base help in the off-season.
7. Trevor Cahill, SP
Cahill's season is especially impressive when one considers that Cahill is only 19 years old and that he won't turn 20 until next March 1. He has had better "swing-and-miss" stuff than did a 19-year-old Jared Lansford at the same level last season and he has had a much better WHIP than did a 19-year-old Vince Mazzaro at the same level last year. Cahill has gone at least six innings in each of his last three starts. He has struggled in the first inning of a number of his starts, but has shown the resiliency to recover and pitch deep into a game despite digging himself an early hole. The A's have to be pleased with the progress that Cahill has displayed thus far this season. They won't rush him, since he is so young, but he might get a taste of High-A the way that Lansford did last season at the end of the year.
8. Landon Powell, C
In addition to being an offensive force, Powell has continued to be a stalwart behind the plate. He is among the leaders in all of the minor leagues in caught-stealings and he has received praise from a number of A's minor league pitchers for his receiving skills and game-calling. Powell adjusted his approach at the plate to use all fields and he has shortened his swing, which has cut down his strikeout totals some. He has also shown a good eye at the plate. Powell is in the best shape of his professional career and the results have reflected his physical improvement. If Powell shows that he can handle Triple-A from both an offensive and defensive perspective, he should enter next spring with a chance to challenge for one of the A's two catching spots.
9. Richie Robnett, OF
Robnett, like Herrera, has all of the skills to succeed, but he hasn't developed the polish to his game that many had hoped to see at this point in his career. He has prodigious power to all fields, but he tends to over-swing, which can lead to a lot of strikeouts. Robnett is a good defensive outfielder with a strong arm who can play all three outfield spots. He has decent speed, but has never been much of a base-stealer as a pro and is only three out of six in attempts this season. Robnett's performance in June was encouraging, as he worked the count better than he did in April and May and that resulted in a much better batting average and OPS. He'll need to continue to build on that performance in July and August. Robnett won't turn 24 until September, so there isn't a rush to get him up to Triple-A this season. However, he'll need to establish himself at Triple-A next season to remain a top prospect. He has arguably the most power of any prospect in the A's system, so the A's will continue to give Robnett every opportunity to succeed.
10. Jared Lansford, SP