The young central midfielder joined on loan from National League side Eastleigh in October 2025, making his debut that same evening against Basingstoke Town. Connor joined Eastleigh as an U16 player, before progressing through the ranks to the senior squad - under the watchful eye of former Dorchester Town player Jason Brookes. Underhill signed his first professional contract last December and went on to make 18 National League appearances for the Spitfires - including a man of the match performance in his first league start at home to Ebbsfleet back in March.