Complex sentence: With Seabiscuit out of action, Smith and Howard concentrated on another of their horses, an Argentine stallion named Kayak II. Pollard and Seabiscuit recovered together at Charles Howard's ranch, with Pollard's new wife Agnes, who had nursed him through his initial recovery.
Split into simpler sentences: With Seabiscuit out of action, Smith and Howard concentrated on their horse Kayak II, an Argentine stallion. Pollard, still convalescing, and Seabiscuit recovered together at Howard's ranch, with Pollard's new wife Agnes, who had nursed him through his initial recovery.