Doncaster-born Nelthorpe began playing for Brodsworth Miners Welfare in 2003, then moved onto Frickley Athletic in 2004 before joining Doncaster Rovers. He signed a professional contract with Rovers on June 28th 2006, going on to play ten matches for the first team, scoring 1 goal.
Craig then signed for Oxford United in 2009, going on to York City, featuring in seven matches for the Minstermen. In this period he also went on loan to Barrow and in 2010 went for a short spell at Luton Town.
Nelthorpe joined Gateshead in the 2010-2011 season, playing 34 matches and scoring 5 goals. In 2012 Craig joined Brigg Town and Frickley Athletic, then going on to Gainsborough Trinity for the 2012-2013 season, playing 32 matches and scoring 5 goals. His next club was Harrogate Town, where he stayed from 2013-2015, playing in 51 matches. Nelthorpe signed up with Matlock Town for the 2015-2016 season, before joining Boro in pre-season ahead of the new campaign.
Craig’s direct style, vicious left foot and pinpoint delivery from set pieces has made him a key player for the club.