Still, the players themselves assert that it's a coincidence, not a consequence.
"I don't think so," said 2008 Derby champion Justin Morneau. "I think if you want it to be an excuse, it can be an excuse for you. We take enough swings and try to hit enough home runs during batting practice, so I don't believe it does. You are constantly making adjustments to your swing during the season anyway. There is no reason you can't go there and do that and then make an adjustment back to where you feel good."
With that said, it's worth noting that Morneau isn't returning to defend his title in 2009. And he did fall off quite a bit in the second half, from a .323/.391/.512 line (batting average/on-base percentage/slugging percentage) before the All-Star break to .267/.350/.481 after. Then again, he had even bigger second-half drop-offs in '05 and '07, so it's not necessarily a result of taking some swings on a Monday night at Yankee Stadium.
Morneau's slide wasn't the only one, though. Over the past 10 years, Derby finalists have seen their average slugging percentage drop from .583 in the first half to .554 in the second. That could be due to players getting out of their approach and messing up their swings. It could be due to some of them getting hurt, as Edmonds did.
Some hitters do acknowledge that the Derby is a unique challenge, even as they deny that it should have any long-range effect.
"It was physically difficult that night, but I don't think it had any affect after that," said 2005 winner Bobby Abreu. "I go through periods when I don't elevate the ball. It comes and goes. It took a lot of energy to do that, but I have long batting practices during the season, too. So I don't think it was a big deal that way, not at all."
The explanation, then, could just be regression to the mean. If you get chosen for the Derby, odds are that you had a very good power first half. And if you had an unusually good first half, chances are you'll have a more usual second half. It's not the law of averages, it's just simple fact: It's hard for even a really good hitter to keep up the pace that some of these guys post in half a season.
"It didn't do anything to me at all," said Garret Anderson, who beat out Albert Pujols in the 2003 final round. "I think it might be a bit of an excuse anyway. Those guys that are in it, I'm sure they take some of those same swings during BP anyway."
That's certainly the case for the man who electrified last year's Derby runner-up, Josh Hamilton. The Rangers slugger put on a spectacular show in the early rounds before running out of gas in the final. He argued that for him, the Derby is no different from a normal day in batting practice.
"Me, I'm going to try to hit the ball out in batting practice anyway, unless I'm working on something," Hamilton said. "Think about how many swings we take in a day. We get here, we hit early in the cage, maybe 25 swings in the cage, then sometimes we have early hitting outside and that's 25 more swings. That's 50 right there. Then we have batting practice, so that's 25 more, then we'll hit in the cage again before the game. So right around 100, 120 swings a day."
Besides, if the Derby is such a problem, how do you explain 2006? Ryan Howard won the '06 Derby in Pittsburgh, cranking 23 homers. He then went on to terrorize the National League for the entire second half. Entering the break, Howard was batting .278 with a .341 OBP and a .582 SLG. After the break he was unstoppable, putting up a ridiculous .355/.509/.751 line that propelled him to National League MVP honors.
"Go back to 2006," Howard said. "That should answer your question right there.
"People try to put that in your head. It didn't affect me in 2006, obviously. But I think it's something that everyone tries to make a big deal out of it. They say people alter their swings or whatever. It's a difference when you're going out there and you know that somebody's throwing a ball at a certain speed and a certain way every single time, and you're trying to put a certain swing on it. But once you get back in the game speed -- it's the same as taking batting practice. You can go and you can basically do everything you want to do in batting practice, but it's like when you get in the game, a lot of things change. The ball speeds up, slows down, curves, dips, dives, juts and dodges. Cuts, everything. So it's still all about getting the right swing and getting the right pitch. So I don't think it really affects your swing in that sense."
And Howard is putting his money where his mouth is. He's participating in the 2009 Derby in his hometown of St. Louis. And why not?
"Sometimes your swing is just going that well to where hey, the ball is jumping off the bat," Howard said. "Sometimes, you may hit it, and it may knuckle if you square it up. I just think that a lot of people, if somebody's not necessarily hitting the ball the way that they were before, hitting the ball out, they blame it on the Home Run Derby."