Complex sentence: Cuthbert used his experience to round up several players from the East, but most of the first-year Browns were St. Louis players: brothers Jack and Bill Gleason, pitcher Jumbo McGinnis, outfielder George Seward, and catcher Tom Sullivan.
Split into simpler sentences: Cuthbert used his experience to attract several players to St Louis from the East, but most of the first-year Browns were St. Louis players. There were the brothers, Jack and Bill Gleason, pitcher Jumbo McGinnis, outfielder George Seward, and catcher Tom Sullivan.