"I've got my BBC commitments and my charity work. I'm also working on getting my Uefa Pro license," he added.
Shearer had been tipped to gain experience at Saints after failing to agree a role at his ex-club Newcastle.
The 37-year-old added: "I'm going to be very busy for the next six or seven months."
"I was with Jason both as an apprentice and as a player. I gather the club's search goes on and I wish them well with that."
When asked by BBC Radio Solent whether he would consider the job in the summer, Shearer replied: "No."