American League manager Ron Washington had planned to use Beckett in the second inning, but after attempting to warm up, he was scratched.
"I could have pitched. I'm just not comfortable going out there and getting hurt in an All-Star Game and costing myself starts in the second half," Beckett said. "I think that's how everybody should be. This game does mean a lot with home-field advantage and everything but at the same time there are some things that are ahead that are a little more important."
Beckett was pulled from his last start last Thursday night after five innings with what the Red Sox called a mildly hyperextended left knee. The right-hander said he did all of his side work Sunday and was cleared to play in Phoenix, and on Monday said he would be available to pitch even if Red Sox management wasn't inclined for him to do so. He said the knee was not an issue.
"It's kind of weird. I was warming up and didn't feel 100 percent," Beckett said. "It's not something I was comfortable with. I don't think I re-injured it but it still definitely has inflammation."
Beckett's absence hurt the AL, which already was missing Detroit's Justin Verlander, Yankees left-hander CC Sabathia, Tampa Bay's James Shields and Felix Hernandez of the Mariners because they started for their teams on Sunday.
"We had to make an adjustment, and that's exactly what the game is about," Washington said following his team's 5-1 loss. "But we were able to get some pitching out there, so we are not going to use not having Josh as an excuse."
Gordon Edes covers the Red Sox for ESPNBoston.com. Information from The Associated Press was used in this report.