By the Numbers: Where did all the pop go?

Last week, we identified half a dozen American League players who are off to slow starts. Inexplicably, each of the featured players has been a Fantasy disappointment, not due to bad luck, but because of a sudden and unexpected dip in skills. This week, we try to solve the riddles posed by six early disappointments in the National League.

Ryan Zimmerman, 3B, Washington: To look at Zimmerman's stats over his first three seasons, you would think he had peaked at the ripe old age of 22 during his rookie year. His OPS has slipped from .822 to .788 to .656 so far this year. Steals have sagged from 11 to 4 to 0 (albeit in just the first 37 games). RC/27 has fallen ... well, you get the picture. Is it already over for Zimmerman before he is old enough to vote in his second presidential election?

Take a closer look at 2007; he was every bit as good then as in his rookie season, but just with a slightly unlucky H/BIP rate. Luck may be playing a small role in his slow start this year, but a power outage is the main culprit. Even so, at the current rate, many of his stats for '08 will closely match those of '07, except he would hit fewer doubles and walk less often. Given the consistency he displayed over his first two full seasons, I would be willing to give Zimmerman a mulligan on the first six weeks of this season. He is a good bet to bounce back and could be a bargain buy right now.

Roy Oswalt, SP, Houston: Few starting pitchers have been as consistent as Oswalt over the last several years. You know he will strike out seven or eight batters every nine innings, post a BB/9 rate around 2.0, and give up very few home runs, resulting in an ERA near 3.00. The strikeout and walk rates are where we expect to see them, but Oswalt suddenly can't keep the ball in the park. He has already yielded 11 long balls, just three fewer than all of last year. A total of 10 of them, however, have been hit in his home park, the notorious "Juice Box." His HR/9 rate is too high to ignore, and owners need to monitor it. However, if he can revert to his usual homer-stingy ways, you can count on another solid campaign from Oswalt.

Ken Griffey, Jr., OF, Cincinnati: Remember when they used to call Griffey, Jr., The Kid? Nah, me neither. He's 38 now, and you have to wonder if this could be just another temporary downturn, or if Griffey's career is rapidly reaching its conclusion. He has finished a season with a sub-.200 Isolated Power only once since 1990. That was the 2002 season, when he missed nearly the entire first half and then spent the second half recuperating from a slew of injuries. Maybe he could bring his power numbers back up, but a third straight year of steady decline in your late 30s is not usually a sign of an impending rebound. If you have Griffey on a mixed league roster, consider dropping him soon, and if he makes the rumored move from Great American Launching Pad to Safeco Field, it is definitely time to move on.

Jeff Kent, 2B, L.A. Dodgers: Two years ago, when Kent was a spry 38 year-old, it looked like he was on the slippery slope to retirement, just like Griffey appears to be now. His Isolated Power fell below .200 for the first time in a decade, and his home run, RBI and runs scored totals all fell by at least 35 percent from the year before. Then Kent bounced back last year with a .302-20-79-78 effort. This year’s dropoff, however, makes 2006 look like a hiccup. Given Kent's age and the dramatic decrease in power and walk rate, it appears that his time as an above-average Fantasy 2B has run out. If you are still rostering Kent, now would be a good time to try to buy low on Rickie Weeks or Kelly Johnson, either of whom are far superior to Kent at this point.

Khalil Greene, SS, San Diego: There are all sorts of places to lay blame for the Padres' woeful start, but no one has been in more of a funk than Greene. After a breakthrough season in '07, when he socked 27 homers and knocked in 97 RBI, Greene has hit a punchless .209 so far in '08. Only one of every four balls in play is turning into a hit, but that's what happens when you hit with typical shortstop power (.101 Isolated Power) but you don't have the speed of a Ryan Theriot (.087 Isolated Power, 28 percent H/BIP). Since Greene's game is devoid of great speed or contact skills, when his power disappears, so does his productivity. He has never experienced this severe of a power drought in his career, so unless he is hurt or pulling a Hafner, there is every reason to think he will work his way out of it.

Bronson Arroyo, SP, Cincinnati: Arroyo's profile is very similar to Oswalt's. His walk rate is up, but it is more than offset by a spike in his strikeouts. He has given up a bunch of homers, mostly in his home park. One key difference, though, is that Arroyo has also been penalized by an extremely high H/BIP rate. Even with his elevated HR/9 rate, if Arroyo had anything close to a normal 30 percent H/BIP, his ERA would be merely bad instead of atrocious. For example, Brett Myers currently owns a 2.2 HR/9 rate, but because his H/BIP is 31 percent, his ERA is almost two full runs lower than Arroyo's. He doesn't yet belong on anyone's roster, but once he gets his HR/9 closer to 1.0, Arroyo would be a nice waiver pickup.

Al Melchior was recently a Fantasy columnist and data analyst for Baseball HQ and will be providing advice columns for CBSSports.com. Click here to send him a question. Please put "Melchior" in the subject field.