Dodgers manager Don Mattingly said that Juan Rivera (hamstring) sounded a little sore after playing his latest rehab game with High-A Rancho Cucamonga on Wednesday. It was previously thought that Rivera would return from the disabled list Friday, but Mattingly isn't so sure, especially after Matt Kemp's recent setback. "We're not going to say he's coming to Colorado and ready to go first day," said Mattingly. "We need to be patient with Juan and make sure we are as sure as we can that he is ready to go."