A Duncan-class battleship could transform Coronel

What changes if a Duncan-class ship replaces Canopus at Coronel?

The Germans likely avoid the fight or face a dangerous long-range engagement against a faster, tougher British pre-dreadnought with heavier guns.

A Duncan-class battleship brought stronger armor and 12-inch guns, along with the ability to hold speed and act as a steadier gunnery platform. A pair of Duncans could shepherd or trap the German squadron, making a straightforward repeat of Coronel far less likely. Rough water would reduce the German cruisers' ability to exploit their nominal speed and lower-mounted weapons. Even one Duncan could force von Spee to avoid battle, while two would let British cruisers help channel the enemy toward a much heavier broadside.