David Ortiz has been in the middle of some of Fenway Park's greatest moments. None of them seemed more important to "Big Papi" than his role in one Saturday afternoon. Ortiz helped the Red Sox honor the victims and the survivors of the Boston Marathon bombings then played in his first game since last summer, a 4-3 victory over the Kansas City Royals capped by Daniel Nava's three-run homer in the eighth inning.