Most football players placed their number following their signature, as is customary. However, some early signatures include "FF" or "4." Favre began placing his number with his signature in 1992. This was due to a contract clause that required him to wear number 4 if he were to remain with the Vikings past his rookie season. Number changes have occurred throughout his career. In fact, there are three times in which he has worn another player's number. In 2001, after suffering two serious injuries (one to his spine and one to his leg) in four seasons, Favre announced that he was retiring from professional football. Before he could hang up his pads, however, he returned for one final season with the New York Jets. He spent most of the year injured but did appear in eight games before being released by the team at the end of the season. Favre signed with the Minnesota Vikings shortly after being let go by the Jets. He agreed to return to Vike Stadium for one final season and put an end to any talk about retirement.