Ramirez, picked in fan voting to start in the AL outfield, has a sore right knee. Minus the Boston slugger, AL manager Ozzie Guillen said he hasn't decided on how he will revamp his lineup.
Guillen and Ramirez shook hands and embraced before the Red Sox played at Chicago on Friday night. Ramirez was in Boston's lineup.
"I respect that he's hurt," Guillen said. "I appreciate Manny told me with enough time to let somebody know because Magglio was playing on the West Coast and we had to let him know right away."
Boston manager Terry Francona backed Ramirez.
"I understand what Manny means to this game, at least I hope I do, but at the same time we're trying to win so bad and I felt strongly enough to try to step in," he said.
"The only thing he may do, and this isn't for sure yet, is see a guy in Miami. In honesty, he's played a lot. I watched him in Tampa the other night and he was kind of ... you can tell it hurt, that's the best way to put it," he said.
Ordonez, on the All-Star team for the fifth time, is batting .307 with 15 home runs and 59 RBI. Ramirez was hitting .310 with 24 homers and 65 RBI.
"Throughout most of the 2006 season, I have been playing with nagging soreness in my right knee," Ramirez said in a statement. "After much consultation and discussion with my team, we have decided that it is necessary for me to rest my knee over the three-day All-Star break."
Oswalt will make his second consecutive All-Star appearance and joins Lance Berkman as the only Astros on the NL squad. Oswalt pitched one inning in last year's game in Detroit.
Martinez missed his start Monday because of a sore right hip and the New York Mets placed him on the 15-day disabled list.
Houston's Phil Garner, the NL manager, asked Oswalt to join the team after learning of Martinez's injury Thursday.
"I'm really excited to be able to take Roy to the All-Star Game," Garner said.
Oswalt (6-5) ranks sixth in the NL with a 3.10 ERA. He's thrown complete games in his last two starts and lost both, the first Astros pitcher to pull off the dubious double since J.R. Richard in 1979.
Oswalt said he accepted the invitation after a conversation with Astros owner Drayton McLane.
"I talked to Drayton a little bit and I think it's in the best interest of me and the team to do it," Oswalt said. "Anytime you get to go, it's great."
Oswalt is the only pitcher who's won 20 games the last two seasons and his 46 victories since the beginning of 2004 leads both leagues. He was the MVP of the 2005 NLCS and is 4-0 in the postseason, the most playoff wins without a loss among active pitchers.
Oswalt said he was a bit disappointed that he wasn't originally selected to the game.
"I thought maybe my numbers would be good enough to go, but it's not all about wins -- it also has to do with popularity," he said.