The Red Sox righthander was scheduled to start the second inning. But his knee, which he hyperextended during his last start, did not feel quite right as he threw in the bullpen.

Because Beckett had promised manager Terry Francona he would not take any chances, he stopped throwing with about 10 pitches remaining in his warmup.

“It’s not something I was comfortable with. I don’t think I re-injured it but it still definitely has inflammation,’’ he said. “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. I think that’s how everybody should be.

“This game does mean a lot with home-field advantage [in the World Series], and everything. But at the same time there are some things that are ahead that are a little more important.

“If it was a regular game I could have pitched through it but if something happened, I would have made a lot of people not look good.’’

Beckett said his knee became stiff during the flight from Boston on Sunday but he did some jogging on Monday and felt fine.

Beckett (8-3) is not scheduled to pitch until Sunday night against Tampa Bay.

“I think it’s really a strong possibility. At worst, we might push it back a day or two,’’ he said.

Beckett spoke to Francona and Red Sox head trainer Mike Reinold, and said neither was overly concerned.

“It was a precaution more than anything else,’’ he said.

Peter Abraham can be reached at pabraham@globe.com.