After looking at some great leaps forward yesterday, let’s flip the coin and look at ten Top 100 Prospects who have failed to live up to expectations-and in some cases, haven’t even come close.

Yonder Alonso, 1B, Reds (Pre-season ranking: 35)

When the Reds selected Alonso in last year’s draft, the confusion didn’t revolve around why they liked him as much as why they liked him better than Justin Smoak. While Smoak is on the verge of making it to the big leagues, Alonso got off to a good start in the Florida State League, but he scuffled at Double-A while showing well below the kind of power that was expected. Concerns about his ability to hit left-handers also remain; while the sample size is small, he’s 9-for-43 against southpaws without a home run. He’ll get little chance to make improvements from there, as a broken hamate bone could cost him the remainder of the season.

Pedro Alvarez, 3B, Pirates (Pre-season ranking: 4)

His disappointing junior year was written off as the result of a broken hand, but what excuses do we have now? Batting .240/.322/.479 across two levels, Alvarez has certainly shown off his tremendous raw power, but it’s come at the price of 87 strikeouts in 288 at-bats, and scouting reports that say he’ll need to move across the diamond to first base sooner rather than later.

Lars Anderson, 1B, Red Sox (Pre-season ranking: 17)

Entering the year as the top prospect in the Red Sox system, Anderson was seen as on the verge of something special, with a possible September callup. Even more disturbing than his .262/.356/.407 line that includes just eight home runs in 275 at-bats are consistent scouting reports from multiple sources that now project him as no more than a second-division starter in the big leagues.

Engel Beltre, OF, Rangers (Pre-season ranking: 68)

All the tools in the world and an assignment to the high-octane California League looked like the perfect formula for a breakout, but nothing has gone in the right direction for him. Beltre’s swing-at-anything approach has led to more advanced pitching simply giving him nothing to hit, thus the miserable batting line .220/.271/.302.

Eric Hosmer, 1B, Royals (Pre-season ranking: 18)

Yes, adjusting the pro ball is a difficult thing, but when you get a $6 million bonus, immediate production is expected. The awaited second-half surge just doesn’t seem to be taking form, as one of the best high school power hitters scouts had seen in years has just four bombs in 251 at-bats and an overall line of .251/.352/.378. Some scouts suggest that he needs to adjust his position in the batters’ box, as he’s so far away from the plate that it’s affecting his ability to hit anything out of his wheelhouse.

Jeremy Jeffress, RHP, Brewers (Pre-season ranking: 72)

You don’t need more than one hand to count the number of pitchers who can match the kind of numbers Jeffress can put up on a radar gun, but he began the year with a profound inability to throw strikes, and just when it seemed like he was making progress back in the Florida State League, his inability to stay away from smoking marijuana cost him a 100-game suspension that will take him well into the 2010 season. It is a sad and stupid waste of talent.

Kellen Kulbacki, OF, Padres (Pre-season ranking: 84)

On a pure numbers level, Kulbacki was arguably the best hitter in the minors during the second half of 2008, but a slow recovery from shoulder surgery cost him the first month of the 2009 season, and he’s been out since the end of June with a hamstring injury. Even more of a matter of concern was his .201/.257/.254 line in 36 games for Double-A San Antonio, making last year look more and more like your classic Cal League mirage.

Michael Main, RHP, Rangers (Pre-season ranking: 66)

A 2007 first-round pick, Main missed much of the 2008 season due to a cracked rib, but he showed tons of potential in his brief return, and as one of the most athletic pitchers in the minors, he oozed projection. A 7.33 ERA at High-A Bakersfield was already greatly disappointing, but then he went down with a mysterious ailment that including exhaustion among other symptoms that doctors have not been able to fully diagnose; there is no timetable for his return.

Mike Moustakas, 3B, Royals (Pre-season ranking: 21)

After a slow start to his pro career, Moustakas was the best hitter in the Midwest League over the last few months of the 2008 season, and seemed poised for big things, but his season at High-A Wilmington has been anything but big. With only one home run in his last 41 games, he’s now batting just .263/.302/.415 on the year, and his defense at third base has received some rough reviews.

Kyle Skipworth, C, Marlins (Pre-season ranking: 82)

The most worrying thing about Skipworth’s .201/.259/.328 line at Single-A Greensboro is the fact that the Marlins drafted him with the sixth overall pick last year as a guy with a reputation for being an offense-oriented catcher. He’s clearly not that, and he’s made seven errors, been charged with 10 passed balls, and thrown out fewer than 20 percent of opposing basestealers, proving that his defense still needs a ton of work as well.