After attending St. Cecilia's RC Technology College (now St. Cecilia's RC High School), Lonergan progressed through the Youth Training Scheme and was offered a professional terms by Preston North End in the 2000–01 season. Lonergan then made his Preston debut managed by David Moyes as a 16-year-old in a League Cup tie away at Coventry City. However, Lonergan made an impression on his debut despite conceding four goals, as Preston North End lost 4–1. Despite this, Lonergan went on to win the Young Player of the Year for the 2000–01 season.