"It scared the [expletive] out of me," Cameron said.
Adrian Beltre heard the scream, too.
"He was in a lot of pain," Beltre said. "I was scared when I saw him [lying] there."
The Red Sox were two outs away from closing out the Kansas City Royals in the rubber game of their three-game set when Mitch Maier, a left-handed hitter, sliced a fly ball down the left-field line. Ellsbury, who was playing straightaway, got a good jump and sprinted toward the line. Beltre, believing Ellsbury was shaded more toward center, leaving him as the only Sox player with a shot at the ball, put his head down and ran back.
Ellsbury only had eyes for the ball as he went into a slide and lifted his glove in anticipation of a catch. Beltre, shocked when he realized too late that Ellsbury was in his path, drove his right knee into Ellsbury's ribs as he tumbled over the outfielder, the ball hitting his glove and falling free.
Ellsbury screamed, then clutched the left side of his chest as manager Terry Francona and trainer Mike Reinold made their way from the dugout.
"He was in a lot of pain when we got there," Francona said, "and he was still in a lot of pain when I came back in here."
You can imagine the relief, then, when Ellsbury returned from an examination by the Royals team doctor and reported that X-rays were negative, and his injury was diagnosed as bruised ribs.
"It's sore, but I'll be fine,'' Ellsbury said. "He kneed me in my ribs so that was the thing I was worried about, a broken rib or something like that. I'm sure there's going to be quite a bit of swelling because it's a little tough to breathe, but I think I'll be fine."
It would appear highly unlikely that Ellsbury will be available for Monday's game against the Twins in Minneapolis, and a reasonable guess is that he may need at least a few more days after that. Hard to imagine the league's top base-stealer running freely with aching ribs.
"I guess the thing is to wake up tomorrow and see how I feel," Ellsbury said. "I know it's going to be really sore tomorrow. I think I'll be all right."
As for the play itself, Ellsbury said, "I'm pretty much going for anything, same for [Beltre]. I don't think we thought both of us would be there, but it was one of those things perfectly between us. I was going to catch it. I was right under it to catch it. I guess it hit his glove and popped out. Just one of those plays."
Asked if he recalled absorbing a bigger hit, Ellsbury said: "I played football when I was younger, but you have pads and stuff and don't take a knee to the ribs. I don't know how it looked, but for how hard he hit me, I think I feel pretty good."
Was this a reminder of why he stopped playing football? "No," Ellsbury said, managing a smile. "I don't mind taking hits. I'll go across the middle."
Gordon Edes covers the Red Sox for ESPNBoston.com.