For prospect watchers, this is the real Opening Day, as after four Eastern League games last night, all ten full-season leagues get their seasons going today. A quick scan of the rosters shows some surprising assignments that either lower or higher than expected compared to the standard development curve. Here’s ten of particular note, as well as some thought on what that assignment may (or may not) say about their standing within the organization.

RHP Tim Alderson, Giants: High-A San Jose

This certainly looks surprising on paper, as the 2007 first-round pick spent his full-season debut at San Jose last year and led the California League in ERA. What you’re actually looking at is a reality of the early part of the season known as the weather factor. A quick look at the forecast for Norwich, Connecticut (home of San Francisco’s Double-A squad) shows nighttime lows in the 30s. You want your prize prospects loosening their arms there, or in the relative beauty of San Jose? Once things warm up, Alderson will move on, as will many other top prospects in the Giants’ organization, such as righty Madison Bumgarner and catcher Buster Posey. If you’re planning a trip to San Jose to see one of the most talented teams in the minors, plan it soon, because it’s not going to stay that way for long.

3B Pedro Alvarez, Pirates: High-A Lynchburg

If anything, this looks a bit low, as there are some expectations for Alvarez to be a part of the big-league club in 2010. Still, the assignment makes sense, as he’s yet to take a professional at-bat. The idea here is to ease Alvarez into pro baseball and begin the year on a roll, with success building confidence, making the adjustments to the upper levels that much easier. Based on the scouting reports this spring, he won’t be spending much more time in the Carolina League.

C J.P. Arencibia, Blue Jays: Triple-A Las Vegas

This one might say something about a timetable, as incumbent big-league catcher Rod Barajas is playing in a contract year. After hitting as many home runs as Matt Wieters last year while playing at the same levels, Arencibia is a highly advanced prospect with plus offensive and defensive skills. The big hole in his game is a hack-tastic approach that generated all of 18 walks last year, but with a start just one level away from the big leagues, he could be up before September.

RHP Andrew Brackman, Yankees: Low-A Charleston

The guy has never thrown an official pitch as a professional, though he did get 34 innings over the winter in Hawaii, so this makes sense. Still, he’s 24 years old and can’t be expected to follow the standard prospect timetable. Like Alvarez, much of this assignment is designed to be a confidence booster, with the hope that he can be ready soon for a move to High-A Tampa, lining him up for the top levels of the Yankees’ system the following year.

SS Starlin Castro, Cubs: High-A Dayton

Castro hit .311/.364/.464 in the Arizona Summer League last year, so this three-level jump to High-A is one of the bigger shocks to be found, especially considering that 2008 first-round pick Ryan Flaherty, a 22-year-old polished college shortstop out of Vanderbilt, will be manning the position at A-ball a level behind him. Castro certainly has the tools-he’s a flashy defender with gap power and a bit of speed, and the Cubs must have seen something in him this spring to inspire such a confident assignment.

OF Desmond Jennings, Rays: Double-A Montgomery

One of the top athletes around, Jennings had a breakout campaign in 2007, but last year he was sidetracked by a non-stop run of injuries, including knee, back, and shoulder issues. What’s surprising here is that when Jennings was healthy, he hardly had the league solved, batting just .259/.360/.412 and following that up with a .231/.326/.359 showing in the Arizona Fall League. This is a bet on Jennings’ tools as well as an outstanding approach that allows him to avoid prolonged slumps. You could put your chips down on far worse things.

LHP Aaron Poreda, White Sox: Double-A Birmingham

After almost breaking camp in the bullpen with the big-league club, why is Poreda heading back to Double-A? It might be a matter of comfort, as the 2007 first-round pick’s strikeout rate rose dramatically at Birmingham last year, as pitching coach J.R. Perdew helped him refine his slider. Poreda’s goal this year will be further improvement of his off-speed offerings, and the message to White Sox fans and fantasy players is that while many scouts still see him as a late-innings power reliever in the end, the organization still wants him to be a starter.

C Wilin Rosario, Rockies: High-A Modesto

The Rockies had big dreams on Rosario in 2007, but he didn’t live up to expectations until last year when, repeating the short-season Pioneer League, he hit .316/.371/.532 while showcasing plus power and an outstanding arm. A multi-level jump to High-A seems like something of a risk for the 20-year-old Dominican, especially in a system that has its share of catching prospects and a young stud already in the majors in the form of Chris Iannetta. At the same time, it’s hard to get off to a bad start in the offensive environs of the California League.

LHP Daniel Schlereth, Diamondbacks: Double-A Mobile

When one drafts a college reliever, one of the goals is to get a quick return on your investment. The Tigers are certainly looking for that from their 2008 first-round pick, as Ryan Perry is in the big leagues, and Perry’s bullpen mate at the University of Arizona is looking to join him soon. After Schlereth was selected just six picks after Perry, opposing batters struck out 20 times against him in 41 at-bats during his brief pro debut, so the stuff to succeed is certainly there, including a mid-90s fastball from the left side.

RHP Jordan Walden, Angels: Double-A Arkansas
The top prospect in the Angels’ system, Walden spent most of 2008 at Low-A Cedar Rapids, putting up a 2.18 ERA in 18 starts before that mark nearly doubled to 4.04 in nine games at High-A. A return to the California League would be the standard path here, but Walden’s fastball should play at nearly any level in baseball; it’s a massive sinker that features plus-plus velocity and reaches the mid to upper 90s. The refinement of his command and secondary offerings will be key to his success (or the lack of it) in the Texas League.

A version of this story originally appeared on ESPN Insider Insider.