"It's hard to compete when you can't be out there," said Mattingly. "With this type of injury, there's not a lot you can do. If you lose eight to 10 days, how many days does it take just to get your timing back? Not a good time to get hurt. You could see it on his face last night. These guys know it hurts your chance."
De Jesus was injured fouling off a pitch Saturday night. Three years after having his promising career derailed by a broken leg suffered in Spring Training, De Jesus was having an impressive camp leading up to the latest injury.
Mattingly had better news on reliever Matt Guerrier, who has been out a week with lower back pain. He said the right-hander has continued to improve and plans to throw off a mound Monday. If that goes well, he could face hitters in a simulated game Wednesday and might be game-ready by next weekend.
That leaves little margin for error to be ready by Opening Day.
Jerry Hairston, who was nursing slight quad tightness Saturday, also was sent home with the flu, but was back in camp Sunday.