One of the more exciting events in a baseball season is the call-up of the hot minor-league prospect. Whether your team is in the middle of a playoff race or 15 games back, it’s like a great plot twist in the long season when the much-heralded future of the franchise arrives on the scene. By blasting some September home runs or striking out the league’s All-Stars, a late-season call-up can quickly become the most energizing player on the team.

Even if they have some success, though, that doesn’t automatically mean that their follow-up effort will be good, as we’ll see with three such players from last season. Seattle’s Felix Hernandez, Atlanta’s Jeff Francoeur, and San Francisco’s Matt Cain all have the potential to be All-Star caliber players – and all showed glimpses of this in their 2005 late-season debuts – but all three are discovering that a hot start doesn’t mean they don’t have to make adjustments to continue their success.

FELIX HERNANDEZ, RHP, SEATTLE
2005: 4-4, 84.1 IP, 2.67 ERA
2006: 7-6, 84.1 IP, 5.02 ERA

To say that fans and analysts were excited when “King Felix” arrived in Seattle last year would be quite an understatement. Hernandez’s filthy stuff, outstanding minor-league record, and the birthday on his driver’s license (4/8/1986) led some to predict the second coming of Dwight Gooden.

Hernandez certainly didn’t disappoint in 2005, posting a 2.67 ERA in 12 starts, with 77 strikeouts against 23 walks. Perhaps even more impressive was the fact that he gave up only five home runs in 84.1 innings while maintaining a 68% ground ball rate. The hits that Hernandez did give up were staying in the park; those balls that were put in play were mostly pounded into the dirt instead of roped into the outfield.

This season, though, Hernandez looks shaky, and currently sports a 5.02 ERA in 14 starts and 84.1 innings. His peripheral statistics are mostly strong – he’s struck out 82 hitters while only walking 28 – but he’s allowed a ton of home runs. With 14 allowed thus far, Hernandez is on pace to allow 32, which is out of line with his career.

The problem seems to be mistake pitches. Hernandez is still inducing a lot of ground balls, and a review of the home runs he’s given up indicates that, as Nate Silver of Baseball Prospectus wrote, “Hernandez is behaving like a 20-year-old pitcher with all of five months of big league experience to his name.”

Blazing fastballs shoved down the pipe may have tormented hitters in Double-A and Triple-A, but those pitches get launched over the fence in the major leagues. Hernandez still has nasty stuff, but he needs to make some adjustments in his strategy and learn how to get outs in varying scenarios to become the pitcher many were anticipating.

JEFF FRANCOEUR, RF, ATLANTA
2005: .300 AVG/.336 OBA/.549 SLG
2006: .246 AVG/.263 OBA/.453 SLG

Francoeur hit the league last year with all the subtlety of an atom bomb. After his first two months in the majors, the Braves prospect was hitting .342 AVG/.378 OBA/.632 SLG with 53 hits and 24 extra-base hits in his first 155 at-bats. He slumped in September but still finished the year with a very respectable batting line.

All in all, Francoeur seemed poised to become the impact hitter the Braves so needed this season. As Braves fans will tell you, things haven’t worked out that way. At press time, Francoeur was hitting just .246/.263/.453. The power is still there (14 home runs, on pace for 33 this year) but he’s struggling in all other phases of his offensive game.

Francoeur’s batting average places him 169th out of 183 qualifying hitters, and he’s struck out 56 times against only five walks (one of which was intentional). As a result, Francoeur’s on-base average is the second worst in all of baseball for all qualifiers, making him the second-best out-maker in all of baseball this year – not a contest ballplayers want to win.

What happened to last year’s stud? If you examine his numbers from 2005, you can see some indications that this was coming. Francoeur ended last season with 58 strikeouts and only 11 walks (he didn’t take an unintentional walk until his 43rd game). He has an outstanding natural swing and impressive raw power, but he completely lacks plate discipline. The scouting report on him had to indicate that he was capable of launching anything in the strike zone, but incapable of laying off balls outside the zone.

Pitchers have adjusted, and Francoeur has not. For the most part, his bat has been neutralized by pitchers who aren’t afraid to throw him balls and let him get himself out. For Francoeur to develop into the All-Star the Braves need him to be, he’ll have to be more selective at the plate and learn to read pitchers as they’ve learned to read him.

MATT CAIN, RHP, SAN FRANCISCO
2005: 2-1. 46.1 IP, 2.33 ERA
2006: 6-5, 77.0 IP, 4.79 ERA

Like Hernandez, Matt Cain was considered the savior of his franchise when he was promoted toward the end of last season. After seven starts and a 2.33 ERA, many fans became convinced that Cain would be the centerpiece of the post-Bonds Giants. In 13 starts this year, though, the young right-hander has put up a 4.79 ERA and allowed 10 home runs. What gives?

Cain’s problems are two-fold. First, the hard-throwing righty doesn’t have much control over his fastball. He’s already allowed 30 walks in 69 innings, and with only 52 strikeouts, his K-to-BB ratio is decent but not dominating. Cain’s other problem is that he is a strong fly-ball pitcher, and a lot of his fly balls are leaving the park.

All the clues were there last year: poor walk rate, flyball tendencies, and an unspectacular strikeout rate. What probably wasn’t noticed last year was that most of Cain’s strong numbers came against the NL West’s weaker offenses. Against tougher competition this year, his weaknesses have been exposed. To achieve his potential, Cain will either have to improve his control dramatically or improve his strikeout rate. One way or the other, he has to prevent the long balls. His present profile simply isn’t good enough to lead a major league staff.

Mr. Gorman is a writer for Baseball Prospectus. For more state-of-the-art analysis, visit www.baseballprospectus.com.