"It caught me off guard," said Indians pitcher Justin Masterson, who used to play for the Red Sox. "That was a nice gesture for Boston. That song more or less defines the Red Sox."
Playing the song was one of many gestures that paid tribute to those killed or wounded in Monday's tragic bombings at the finish line of the Boston Marathon. Before the Indians hosted the Red Sox, who picked up a 7-2 victory, both teams lined up along the infield lines and took part in a moment of silence.
That was a moment that stuck with Indians manager Terry Francona, who managed the Red Sox from 2004-11.
"I'm not sure how to describe the feelings," Francona said. "You're sad and you think of a lot of things. We get so wrapped up in a baseball game, because it's so important to us, and then you look up and you realize why you're having a moment of silence. If you need perspective, it gives it to you in a hurry."
The teams also wore black arm bands in honor of Monday's events in Boston.
Other teams around the league, including the Yankees, also played "Sweet Caroline" during their games. At Yankee Stadium, the words "United We Stand" were displayed atop the ballpark with the logos for the Yankees and Red Sox side by side.
"I think it's a touch of class by, not only Cleveland, but every Major League city around baseball," Red Sox manager John Farrell said. "I saw the sign on the front of the facade at Yankee Stadium and I think the fact that they played 'Sweet Caroline' in the third inning there, I think it's a touch of class by all of Major League Baseball to acknowledge this."
Jordan Bastian is a reporter for MLB.com. Read his blog, Major League Bastian, and follow him on Twitter @MLBastian. This story was not subject to the approval of Major League Baseball or its clubs.