In the summer of 1993, Manchester United won the title and then signed Roy Keane in a British record transfer. In 2001, United won the title and then bought Ruud van Nistelrooy. In 2008, the summer after winning the Premier League and Champions League, they signed Dimitar Berbatov not because they really needed him but because they could.
Each time, Alex Ferguson took steps not just to maintain the gap to their rivals but to grow it. Each time, United defended their Premier League crown.