Upton is hitting .210 on the season -- .154 in May -- and Pena is batting .186 on the year and just .127 this month. The two have proven to be more than capable at the plate when they find their swings, so Maddon decided to sit Upton and move Pena behind catcher John Jaso and designated hitter Hank Blalock.
"They're struggling, both of them," Maddon said. "It's just about strike zone organization, attacking the pitch that you can hit, laying off the one you cannot. A lot of it is confidence right now. When you get into a bad run, a lot of it is confidence."
Maddon said Upton might be out of the lineup Thursday night as well, though he won't hesitate to bring the speedy center fielder in as a defensive replacement. Maddon had "a nice conversation" with Upton before the game, explaining that he thought Upton was pressing too much. That self-imposed pressure, according to left fielder Carl Crawford, might actually make it harder for Upton to match his previous success in the batter's box.
"He wants to come back and play good, and he's been working hard to try to do that," Crawford said. "But sometimes you try too hard, get tense at the plate. You're not relaxed at the plate. That could be the case."
Pena, meanwhile, was moved down in the order due only in part to his struggles. Jaso's impressive offensive numbers and Blalock's past performances against Wednesday's Red Sox starter, John Lackey, made the decision a little easier on Maddon.
Maddon said he isn't concerned about Pena's average, and he understands that the power-hitting first baseman is somewhat of a slow starter -- he's done this in previous years around this time. However, he wants Pena to start accepting that he will hit into outs where other players will get on base due to the shift opponents use against him.
"Once he gets a couple knocks, his confidence will be right back to where it needs to be," Maddon said. "I'm just trying to monitor both of those guys, because they're so important to us. Furthermore, the guys that have stepped in in these different moments have done well for us. And that's part of keeping everybody during the course of the season."