It shouldn’t matter as much as it seems certain to matter Friday, when the Royals meet the Red Sox at Fenway Park in the first ballgame in this city since Monday’s tragedy. It’s only baseball. But Royals reliever Bruce Chen was on the mound on Sept. 21, 2001, at Shea Stadium as the starting pitcher for the New York Mets in their first home game following the 9-11 terrorist attacks. He has an idea of what to expect. “There are going to be a lot of emotions,” Chen said, “and the fans will have mixed feelings. They won’t want to be there, but they’ll also want to cheer for their team. “The game is something that gives them hope and is something that helps them to keep going. We’re all concerned about the security, but one of the things we’re doing is trying to help the city get back to a sense of normalcy. “Right now, all they see is bad, bad, bad. If you can go back to what you used to do, even for a short time ... it’s a small step, but it helps.” Details are still emerging from the bombings Monday near the finish line of the Boston Marathon, which serves as the centerpiece of the city’s Patriots Day celebration. Those festivities always include an early start game at Fenway Park. The Red Sox had already pulled out a 3-2 walkoff victory over Tampa Bay when the explosions killed three and injured more than 170. “It’s a pretty cowardly act by the people who did it,” said reliever Tim Collins, who grew up in nearby Worcester. “I didn’t have family members there, but a lot of people did. That’s going to be a tough time for them.”