Taijuan Walker is (I believe) the YOUNGEST player in the Midwest League.
He was already ranked as our #4 prospect going into this season...the question is gonna be how far into the top 100 / top 50 prospects he clumbs.  Somebody (*cough* John Ramey *cough*) is getting a bonus for correctly answering the question, "Which kid available with the 42nd pick is gonna take off like greased lightning with a little pro instruction?"
I'm lovin' his consistency and results, especially with his stuff.  He's not getting anybody out with smoke and mirrors.
In less pleasant news, Brandon Maurer hasn't pitched in 11 or so days, so I'm concerned about him.  Haven't heard anything, though.  He's having a phenomenal year too, so hopefully he's all right and is just taking a turn off in the rotation.
Shipers got lit up, but Landazuri started off decently.  Everett has some interesting arms this year, that's for sure, with Campos leading the crop.
~G

17-year-old Martin Estelion Peguero (now going by Martin, apparently) was ranked as high as #4 on some prospect lists as a record-setting Dominican bonus baby.  For undisclosed reasons, his bonus was later sharply reduced.  He went 0-for-4 in his debut in rookie ball, but -- he was hit by a pitch and then stole second and third, so he has 2 SB after one game.  Peguero played SS.
17-year-old Phillips Castillo is another bonus baby, and even younger (born in February of 1994) ripped off 3 hits, including 2 doubles.  A very promising start.  Castillo was in LF. 
Then there's Jochi Ogando, who is barely 18 but listed at 6-5, 210.  From the same scouts that brought us Michael Pineda, so let's hope they know what to look for in huge righthanders.  Ogando went 2.0 IP with 1 H, 0 R, 0 BB, 3 K in his stateside debut.  Like Pineda, he pitched in the Dominican Summer League at 17, but he did not show anything close to the command that Pineda has always had.
18-year-old Guillermo Pimentel will have his 2011 debut tonight at Pulaski.  Pimentel was last year's 17-year-old sensation, with a .451 SLG and 6 triples in 51 games, but it's best not to mention his eye ratio (OK, I will: 5 BB/58 K, ouch) -- there is a lot of upside however.
Finally, I touted 19-year-old Jordan Shipers making his Everett debut (2010 draftee bought out of a college commitment with an $800K bonus), but he was not sharp, giving up 7 H and 6 ER in 3.2 IP, but he did have 5 K.  Everett is an aggressive assignment for teenagers, the success of Taijuan Walker one level higher notwithstanding.

http://www.minorleagueball.com/2011/6/18/2230565/minor-league-notes-june...
 
Long and short of it he says that Walker is a top 50 prospect and a top 20 pitching prospect.  Not bad for a supplemental 1st rounder.

but a quick search did not turn up the reason.

We have three really interesting latin bats, not two, though right now Pimentel has an edge since he was signed a year earlier and has had more state-side instruction.  Pimentel's bat is described by Pedro Grifol as follows:
http://seattletimes.nwsource.com/html/thehotstoneleague/2015167726_frida...
"He's down here (in Arizona) and player great (in extended spring training). He's hitting about .290, seven doubles, four triples, four homers, in only 50-some at-bats. He's itching to go out and play short season. I can't wait to see him go out and play short season. It's an electric bat. He's a free swinger right now, which is something he'll have to continue to work on. They tell me he's really getting better. He makes contact, but he's going to have to shrink he strike zone -- know your zone and where your strength is. If he can do that...it's an electric bat. There are other parts of his game he needs to improve; his baserunning needs work, his outfield throwing arm -- all things that are a little below average. But his bat is electric." Note: Pimentel, one of the key recent international signees by Bob Engle out of the Dominican Republic, is just 18. He is likely to go to one of the two Mariners' short-season teams, Everett or Pulaski, which start play in June. "Either would be a good place,'' Grifol said. "He needs to go under the lights and start to shine in minor-league parks."

His bat is three-times electric?  I guess you don't like it that much, Pedro... *laughs*  You see him swing and it's astonishing.  His pitch recognition isn't there yet and he still feels like he has to swing at everything, but I'd love to see him take it to the App League with a vengeance.
Phillips Castillo, though, was paid what Pimentel was ($2-ish million dollar signing bonus) and is a better fielder from what I've heard.  They love his bat too, and he was considered the top power bat in the 2010 IFA class (while Peguero was the top player available period, until that mysterious bonus reduction).
Martin Peguero, Castillo and Pimentel - hopefully one of them works out for the money we paid for em.  I'd take more than one.  Please, let one of them know how to take a base on balls...
~G

So Peguero, Castillo and Burin will all be in the same lineup.
Burin is the 19-year-old switch-hitting Brazilian 2b who got 50 H, 14 doubles and 19 walks in just 31 games in Venezuela, and with only 12 strikeouts.  Leading me to call him the "Ackley of Sao Paulo."
 

We have several interesting bats in the minors, but nobody that we can trust yet to be the next All-Star bat coming up through the ranks (making the 2nd in a decade, with the first being Ackley.  Okay, the first was Choo, but shaddup about that).
Most of our hitters are second- or third-tier guys.  We have our backups and our complementary players, but few game-changers.  Kyle Seager has value, but he's not going to be a middle-of-the-order guy.  He's no Ackley / Lawrie / Harper / Trout type prospect.  And the Franklins and Catricalas of the system haven't been able to prove one way or the other which category they fall into.
I'm very, very curious to see what the 2011 draftees bring to the table in that regard.  If Paolini can stay at second, or Miller can remain a shortstop, and they can hit in the vein of their college numbers, that could be quite something.
But Castillo or Pimentel working out is on another level, as both guys should have remarkable power if they were to pan out.  I did an off-the-cuff assessment of a high-percentile estimation of the upper expectations for our minor league hitters. 
Ackley - Robin Ventura at 2B
Liddi - Tony Batista (though this mark is moving up)
Peguero - Wily Mo Pena
Seager - Adam Kennedy
Shaffer - Shannon Stewart
Franklin - Ray Durham
Carp - Glenallen Hill
Tenbrink - Trot Nixon
Catricala - Todd Zeile
...
 
And it's not a bad list.  Now, ANY system you look at should have a list like that of what players would look like if they could reach their higher projections instead of the middle or lower ones.
 
But even with that obscenely-rosy view of the system we don't have expected crushers there, certainly not at the upper levels. Maybe Liddi if he becomes more Glaus than Batista.
 
That's another reason I badly want to drop $1.5 million or so in the lap of Cron, a true slugger, to buy him out of his college commitment.
 
We need a Cron, or a Pimentel, or a Castillo to come through for us, so that when we're looking at losing Smoak to FA we have another guy who can pummel the ball and fit into the MOTO all ready to go.
 
This is why I desperately wanted Rendon - to pad the ranks of the good average, great OBP, 35 doubles / 20+ HR hitters that we have, which are nearly extinct in our system currently.
 
So now we need to add another hitter from outside the system in the meantime and wait for the teenagers to hopefully blossom.  You too, Vinnie and Nick - no slacking.
 
Pitching surplus is divine, but arms get injured and never recover.  Bats are more constant.  I'd like some.  TIA.
 
~G

Not really about the 18 year olds (yet) but there's some movement in the system now that the All-Star games have happened (or will soon in the case of AAA). 
Kyle Seager has been promoted to AAA, and Nick Franklin has made it to AA Jackson.  A little surprised about Franklin, who's been a bit static this year and still struggles mightily against lefties, but either they saw what they wanted to see and felt like challenging him, or they wanted him to get with a different batting coach.  Something. ;) Should be an interesting time-share at SS/2B with Triunfel for as long as he's there too. 
And Seager's value keeps growing.  Maybe we'll just use him at 3B next year instead of  going outside the system.  I don't expect that, but stranger things have happened.
There were 7 Jackson Generals in the All-Star game, which was nice.  Mostly pitchers - congrats to Erasmo, Carraway, Grube, Kasparek (boo for the injury) and LaFromboise. Lotta soft-tossers, but we've had very interesting pitchers to go with a couple of hitters (Seager and Shaffer).  Shaffer hit in the HR derby, which was funny since I don't think he's 200 pounds in concrete boots.  He's a leadoff hitter until his power showed up this year. 
Also, Paxton and Liddi were named to the Futures game.  Liddi's not a surprise.  Paxton was, at least for me, with only a handful of innings under his belt.  He was deadly in the All-Star game though, and I'm hoping for a promotion for him shortly as well.
Wilhelmsen's getting properly stretched out as a starter now in AA, so that's good to see (back-to-back games of 6 innings).   Robles has come back in the last week (at High Desert) and is trying to get the rust off after his surgery. Beavan's throwing well (at LAST). Churchill says he's still 89-92, so hopefully he's figured out better control of his pitches.  Last 3 starts: 21 IP, 15 hits, 4 runs (3 HR but 2 were in Colorado), 18K / 5 BB.  His ERA for June is 1.85 with a 4:1 K:BB ratio.  Nice to see. 
Paolini and Pimentel are hitting well in Pulaski in their first couple of games, but I don't weight batting lines in Pulaski as meaning much of anything.  Still their power in the early games is good to see.  Now we'll see how they do with plate patience and batting eye.
And can I give a shout-out to Tony Butler?  After a series of injuries and bad fortune that have nearly destroyed his baseball careeer, he came back to the team that drafted him and took a stab at short-season while trying to get his arm to be effective again.
2 starts, 10 IP, 1 run, 4 hits, 14K/ 3BB, and a chance.
He blew his arm out halfway through 2008, missed basically all of 2009, was terrible with his command in 2010, giving up 10 runs per 9 in the process.
I'm glad for a good start for him. After a long and brutal road back, it's got to be nice to get a couple of good starts under way immediately and feel like maybe your career isn't quite done yet.  He's still just 23 and not even the oldest pitcher on his team.
I love a good comeback story.  Best of luck, Mr. Butler - and may all our prospects have a great second half.
~G

9.0 IP, 2 H, 2 ER (2-run homer), 1 BB, 7 K
Of course, that complete game with 3 baserunners brought his K/9 down to 11.4 (measly 7 K, hmmpf).
19th birthday is a month away.
[Edit: didn't see that G beat me to it with a much better comment.  Go there instead.]
Also of note: 4th-round pick C John Hicks has 4 hits in his first 10 pro ABs at Clinton.
Credit where it's due: James Jones last 19 games -- .296/.354/.507, but he has a lot of ground to make up after a horrible start.