In 2003, Boswell had been ranked in the world's top-10 for two years and had reached a career-high ranking of World No. 4, when a mystery back ailment forced him to stop playing. He returned to the professional tour in 2005. On his return, he won six of the tour's lower-ranking tournaments in a row, and two further lower-ranking tournaments later in the year. He broke back into the world's top-20 in 2006 and the top-10 in 2007.