Beckett was scratched from his start on Monday night due to muscle spasms. His back tightened on the plane from New York to Boston Sunday night and he felt pain on Monday.
"I think you're making a mountain out of a molehill," Beckett said before Boston's game against the Toronto Blue Jays on Tuesday. "It's not a big deal at all."
Manager Terry Francona said Beckett's back spasms were in the upper left portion of his back. Beckett said the areas where he was injected are called "trigger points," and that injecting into the muscle rather than the joint is far less potent, "because there's no cartilage in muscle."
A few players who also have had cortisone shots in the past said they were advised not to have more than one every few weeks but it is not a uniform rule. One player told ESPNBoston.com that he once had three shots in three straight days -- not with Boston -- only out of necessity to be able to play.
Since the shots were in different areas of Beckett's back, it's a different situation than a player having multiple shots in the same location. Beckett also added it was the first time he's had a cortisone shot this year. The last shot he had was last fall when he had an oblique injury, but he said the injuries are not similar.
"No, it was so much different," he said. "It was just something that you wake up with. It wasn't like I felt anything when I was throwing. You wake up and you're locked up."
He plans on making his next scheduled start, which would be Saturday against the Cleveland Indians. Beckett is 16-6 and has already pitched a career-high with 207 1/3 innings.
"I don't want to take anymore time off," he said. "It's that time of the year where I can't. I don't want to go 20 days without pitching and then pitch in the playoffs."
Amy K. Nelson is a staff writer for ESPN.com and ESPNBoston.com. You can reach her at email@example.com or at twitter.com/amyknelson.