The offensive explosion of the past decade may be waning these days, but a slugging percentage over .600 is still a must to top the list of major league mashers. So what can a player who hits a homer once in a blue moon do for a ballclub? Is there even any room in today’s game for the player who regularly gets on base, but would only be invited to the home-run derby to keep score?

There are 16 players this season with a slugging average below .400 and an on-base average above .350. Some of them, like Philadelphia’s Jim Thome and Houston’s Jeff Bagwell, are injured sluggers who usually post considerably higher slugging percentages. Once we eliminate those anomalies, we’re left with a short list of players who get on base significantly more than an average player, but who rarely make it past first base without the aid of whoever is hitting next. That short list contains three of this year’s All-Stars, players who were deemed worthy of representing their team and league despite some of the worst power numbers in the game. We call these guys “Punchless Wonders.”

Though Dodgers second baseman Jeff Kent deservedly started the All-Star Game in Detroit two weeks ago, the more interesting season is being enjoyed by his in-game replacement, Florida’s Luis Castillo. At the break, Castillo was hitting .331 AVG/.426 OBA/.407 SLG, with 40 walks against just 17 strikeouts. Just barely into the second half, he’s slipped to .309/.402/.381, but he’s still on the verge of having a historically unique season. Only 35 players in the history of the game have posted a .400 OBA in the same season they posted a SLG average below .400. Castillo is the only active player to have done it, and could do it a second time if he continues at his current pace.

To get a sense of what that means in terms of runs, we’ll turn to a Baseball Prospectus metric called Value Over Replacement Player (VORP), a measure of the number of runs a player is worth relative to a freely available alternative at his position – like a Triple-A call-up or bench warmer. Castillo has a VORP of 19.2, despite a SLG of just .376 (which is 19 points higher than his career average). As the weekend came to a close, Castillo ranked ahead of such noted sluggers as Ryan Klesko and Larry Walker in VORP.

Castillo’s strength is his ability to control the strike zone; this is the third consecutive year he’s on pace to finish with more walks than strikeouts. He is also among the league leaders in pitches seen per plate appearance with 4.0, a good indicator of a fairly discriminating batting eye and a useful tool for wearing pitchers down and getting into opponents’ bullpens. Although leg injuries have worn away his speed, Castillo is still a very productive hitter despite hitting mostly singles, largely as a table-setter for Carlos Delgado and Miguel Cabrera.

Next on the list of Punchless Wonders is White Sox outfielder Scott Podsednik. 83% of Podsednik’s hits this season have been singles; he also has 16 doubles, with no triples or home runs.

There was quite a bit of off-season disagreement about which Scott Podsednik would show up in the Sox’ remade lineup – the one who hit .314/379/.443 in 2003, or the one who hit .244/.313/.364 in 2004. It turns out it was a bit of both, as he has pushed his batting average up substantially, with his SLG declining sharply. Still, Podsednik has been a solid addition to the Sox’ lineup this year, hitting .289/.357/.341 in 314 AB, with 50 stolen bases against just 10 times caught stealing.

Small-ball devotees point to his 50 stolen bases as a positive contribution, and though the stolen bases do have value, they don’t have as much as one might think. Take last season, for example, when he was getting on base at an underwhelming .313 clip. When you paired his 70 stolen bases with his abysmal batting line, his VORP of 19.3 meant he was about as valuable to his team as Anaheim’s fourth outfielder, Jeff DaVanon. Much of Podsednik’s value is presumably tied to his stolen bases, but the perceived value of stolen bases is much higher than the actual value.

The Cardinals’ David Eckstein earned a spot on the All-Star team for his .284/.358/.358 line in the first half, and has compiled a 16.7 VORP so far. Mets fans might be intrigued at the notion that, after correcting for the discrepancies in their plate appearance totals, Eckstein has been about as valuable to the Cardinals as Jose Reyes has been to New York. Eckstein is quite selective at the plate, and his 41/23 BB/K ratio shows excellent command of the strike zone. Even with all those walks, though, his on-base average isn’t that much higher than his batting average, so he’s not quite at Castillo’s level of production.

Eckstein’s former infield mate, the Angels’ Adam Kennedy, is also contending for our Punchless Wonder crown with a .330/.374/.396 batting line in 246 plate appearances, good for a VORP of 16.0.At first glance, that looks like an impressive batting line, but several warning signs exist just under the surface.

On-base average is a quick-and-dirty indicator of plate discipline, but just eyeballing OBA levels can be a bit misleading. Kennedy sees the fewest pitches per plate appearance of anyone in this group; at just 3.62 P/PA, much of his value is derived from his batting average, as he doesn’t work counts in his favor. While players like the Reds’ Adam Dunn can maintain the bulk of their value while posting middling batting averages, Kennedy cannot. Dunn maintains a high OBA and SLG despite a low batting average, and any spike in BA is an added bonus. Kennedy’s OBA and SLG are tied directly to his batting average, and any dip in batting average impacts the other two categories significantly. Since batting average is a more unpredictable stat than walk rate, there’s some downside to Kennedy’s seemingly impressive numbers.

So who will emerge with the punchless wonder crown? With much of Eckstein’s value tied to his staying in the lineup every day, a healthy Castillo looks like the favorite to deliver the most value to his ballclub. These players may not obliterate opposing pitching the way an Albert Pujols or Alex Rodriguez can. But even in this swing-for-the-fences era, there’s still a place for the little guy.

Mr. Erhardt is a writer for Baseball Prospectus. For more state-of-the-art commentary and information, visit baseballprospectus.com.