Jeff Keppinger, leading LVP contender. (Carlos Osorio/AP)

Over the winter, when the Chicago White Sox signed veteran infielder Jeff Keppinger to a three-year, $12.5-million deal, it seemed reasonable. The third-base market was thin, and Keppinger could play just about anywhere in the infield. No problem.

But Keppinger is hitting .237. Not the worst you’ve ever heard? Right. But consider that in 358 plate appearances, he has just 14 walks, seven doubles, one triple and two home runs, and we give you – drumroll, please – 2013’s worst offensive player.

Keppinger has played in 90 of the White Sox’s games, and those 358 plate appearances are enough to qualify him among the league leaders – except he’s far from the top. His on-base-plus-slugging percentage of .546 ranks him last – by a wide margin – among those who had played so frequently.

And yet Keppinger might not be the most egregiously overused offensive player of the season. Kansas City shortstop Alcides Escobar has appeared in 110 of the Royals’ 112 games, racking up 463 plate appearances. His OPS: an anemic .573, with 15 walks all year.

Escobar and Keppinger are just two of five players who could be considered regulars who have an OPS of below .600 – the new-age Mendoza line. Pete Kozma of the Cardinals (.573), Darwin Barney of the Cubs (.578) and Adeiny Hechavarria of the Marlins (.588) join them there.

But with two months to go, how potentially bad are these seasons? Horrific. In the past 20 years, only Matt Wallbeck of the Twins, in strike-shortened 1994, and Cesar Izturis of the 2010 Orioles have posted a worse OPS than Keppinger (.530 and .545, respectively). Indeed, in that timeframe – a span that includes 3,057 individual qualifying seasons – only 19 times has a player posted an OPS under .600 over the entire season, and never more than three in the same year.

Now, there could be five such players in the same season – a two-month sprint to see who might be LVP.

The most amazing appearance on this list – wait for it, Nats fans – might be Kozma, St. Louis’s shortstop. Last October, he … oh, you know. But he’s the only player on this list of infamy who is in the thick of a pennant race (with apologies to Escobar, whose Royals have gone 16-4 since the all-star break to get within shouting distance).

Kozma, though, may not stay in position to win the LVP. Kozma has started just three of the Cardinals’ last seven games, appearing more frequently as a defensive replacement. Daniel Descalso has 20 starts at shortstop this season, and considering he’s hitting .304 and slugging .652 in August, it’s possible he’d get more time, and Kozma less, as the Cardinals try to catch Pittsburgh in the National League Central.

Either way, as the MVP races in both leagues crystallize, don’t lose sight of something even more rare than hitting 40 homers or driving in 120 runs – players allowed to remain in the lineup, day in and day out, despite hitting terribly.