Kosuke is out of the lineup tonight against the Astros because Mike Hampton, a lefthander, is starting for Houston. In a way, this doesn’t come as a surprise. At the start of the season, Lou said he was going to platoon Kosuke and Reed Johnson, and he’s pretty much done so when he’s had the opportunity.

But in another way, it is a surprise. At the start of the season, I think everyone, myself included, thought Kosuke wasn’t going to have a good year. Yet he entered tonight’s game hitting .300/.436/.525. So far he’s been great with the bat. He hasn’t been great in center field, but he seems to be getting better at it, and he’s only played 120 innings there.

Platooning Fukudome and Johnson isn’t all bad. The Cubs suggested that one of the reasons for Fukudome’s struggles last season was because he was used to a shorter schedule, and because he had been injured in 2007. So basically, he got tired. Obviously, if he’s platooning, he’ll get some more rest.

And what’s more, Reed Johnson is a great platoon candidate. Johnson is a career .283/.344/.408 hitter. That’s not good at all, though not bad for a center fielder. Johnson is also not a good defensive center fielder, though, even though he has a tendency to make some flashy plays. (Remember, you don’t remember the diving catches he misses, just the ones he makes.) Over the course of a full season in center field, Johnson would cost you about 15 runs with his glove. That’s not doing anything to help with those lousy offensive numbers.

But against lefties, Johnson is a .310/.375/.456 hitter. That’s better than Andre Dawson’s career numbers (although with slightly less power), and a lot of Cubs fans will tell you Hawk should be in the Hall of Fame. So if you only bat Reed against lefties, he’s actually a pretty nice player.

The problem is, Kosuke himself isn’t a very good platoon candidate. For his career, he’s hit .263/.370/.399. So he gets on base against all pitchers as much as Johnson does against lefties. And although he hasn’t played a ton against lefties, Kosuke hits them to the tune of .277/.370/.377. That’s not substantially worse than his career numbers, and he’s no more likely to make an out against a lefty than a righty.

I guess what it comes down to, then, is whether you think Kosuke’s numbers this year are for real. I don’t think he’s going to keep hitting like he is this season, but I think he’s going to end up with a significantly better season this year than he had last year. And if he does, it just doesn’t make a lot of sense not to play him every day - you can expect him to put together better at bats than Johnson, and he just has better physical tools to make plays in the outfield. Johnson ought to get plenty of work spelling Fukudome, Bradley and Soriano when they need a game off, but there’s really no reason Fukudome needs to sit every time a lefty starts against the Cubs, especially given the shortage of right-handed bats the Cubs have on the bench.