The pressures of racing and designing the car took their toll on Donohue. By 1973, the "Captain Nice" nickname he had earned earlier in his career was being supplanted by the nickname "Dark Monohue". Donohue announced that he would retire from racing after the 1973 Can-Am season. In addition, the horrific events at the 1973 Indianapolis 500 and the subsequent death of his friend, Swede Savage, pushed him to quit. His retirement was short-lived, however, as he was lured back to full-time competitive driving by Penske when he formed a Formula One team, Penske Cars Ltd, to compete in the final two events of the 1974 Formula One World Championship, and to continue competing in 1975 with the new Penske PC1.