Manager John McGraw’s Giants received an astonishing performance in 1912 from lefthander Rube Marquard, who set a modern major-league record by winning his first 19 decisions. Marquard finished with 26 victories. Christy Mathewson won 23 games. Rookie Jeff Tesreau was a key find, winning 17 games, leading the league in earned-run average with 1.96 figure…