McGuire was never fined or ejected. In 1900 his teammates began calling him Deacon because he was so straight-arrow. He was also known as Pinch, for his timely hitting. Pinch hit .341—going 14 for 41—as a pinch hitter, and he became better with age. After his 40th birthday, he was 6 for 9 coming off the bench.
McGuire first managed in the latter half of the 1898 season for Washington. He had little success that year (19-49) or, indeed, thereafter. In all, he managed one full season and parts of five others. His career record was 208-289.
In 1899 Baltimore manager Ned Hanlon and a partner made a stock-transfer deal with the owners of the Brooklyn Dodgers that left Hanlon and his partner with a 50% ownership of each club. Hanlon, who had led the famed Oriole teams of the early 1890s to three straight National League championships, resigned his position in Baltimore and named himself the Brooklyn manager. He brought Wee Willie Keeler and four other Orioles with him and turned the Dodgers into contenders. In July Hanlon traded two players to Washington for McGuire, who, becoming a player again, hit .318 and helped Brooklyn to the first of two straight championships. The Brooklyn Daily Eagle, for one, hailed the trade. "McGuire has always been looked upon as one of the best catchers in the league," the paper said, "while he has no superior as a coacher of pitchers and for steady and uninterrupted work."
But by 1902 McGuire was back on the road, playing for Detroit and the New York Highlanders before accepting managing posts with Boston and Cleveland. In 1912 he became a scout for Detroit. That May, Tiger star Ty Cobb pummeled a fan during a game and was suspended indefinitely by American League president Ban Johnson, who hadn't heard Cobb's account of the fracas. Cobb's teammates threatened to strike if the suspension wasn't lifted.
One day later, with the suspension still in force, the Tigers changed out of their uniforms and left Philadelphia's Shibe Park. To avoid the $5,000 league fine for a forfeit, Tiger manager Hughie Jennings combed the local sandlots, recruiting college students for the game with the Athletics. To strengthen his motley lineup, Jennings added McGuire and another Tiger scout. The paper Tigers lost 24-2 to the likes of Eddie Collins, Home Run Baker and Herb Pennock. McGuire went 1 for 2, drew a walk, scored a run, had three putouts, three assists (and two errors), and thereby made the record book with his 26th "season" in the big leagues.
From 1913 to '24 McGuire scouted for the Tigers. In '26 he coached the team at Albion College and then retired to his farm on Duck Lake outside Albion. In the fall of 1936, at 72, McGuire died of pneumonia and was buried at the Riverside Cemetery in Albion. Atop his tombstone two slender bats are crossed in tribute to the young iron-molder who became baseball's iron man.