Mattingly had Juan Rivera start at first, Elian Herrera in left and Ivan De Jesus serving as designated hitter.
"James was really sick when he woke up," said Mattingly. "He'll be here around game time, but I won't be bringing him in to pitch in the seventh inning."
Loney's desire to pitch notwithstanding, Mattingly said he also thought about using regular catcher A.J. Ellis as designated hitter. Ellis had the day game after a night game off.
"If Ivan is going to be a pinch-hitter guy, he's got to stay sharp," said Mattingly. "But this happens to a National League team [in Interleague Play]. What we're doing today with the DH is because we're not equipped to have a DH. We're just not. Bobby Abreu can be a DH type, but he's played two games in a row and we've got to keep him fresh. It's all part of balancing the roster right now."