In late 1966, Peter Green had the job of replacing Eric Clapton in John Mayall's Bluesbreakers. Mayall told his producer, "He might not be better [than Clapton] now. But you wait... he's going to be the best." Soon, with the original Fleetwood Mac, he was Britain's most progressive blues guitarist, with a Chicago-informed aggression heightened by the melodic adventure on albums like 1969's Then Play On. Green soon entered a dark age of mental and health problems, returning in the Nineties with more subdued but recognizable gifts.